Before you read one sentence of this guide, know that it only covers legitimate walling. I'll discuss estimating a player's movement patterns, using sound effectively, using sight effectively (which is surprisingly rare), and using your radar. With practice, you will be killing players through walls, or at the very least softening them up for your team, on a regular basis, at several different spots on CS_Assault, whether you're a T or CT. Some people will call you a hacker when you do this. Some people will complain. I do NOT support cheating in any way, shape, or form, nor will I ever. An educated, experienced player knows the difference between a cheater and someone who has learned to use every single aspect of CSS to his or her advantage. If you cheat, you will be caught. Now, onto the fun stuff.
This guide isn't for everyone.
Generally, Assault regulars will use the same spots when they play, because we're creatures of habit, even if these spots are generally ineffective. Just how a lot of the regulars on 108.4 know I'm at the red crate 99% of the time I'm a T. Use that to your advantage. CTs are at a disadvantage on Assault, because obviously, the Ts are expecting them to come in. Turn a disadvantage into an advantage every chance you have. They know you're coming. So kill as many as possible before you go in. What do I mean, exactly? A little thing called walling. And no, you don't need a "wallhack" to wall effectively. All you need is practice and a gun with enough power to get the job done through a bit of steel. The M4 is a poor option for this, because it can take up to 12 hits to deal over 100 damage through a wall, assuming you score body/limb hits. If you're able to score headshots, more power to you. We're talking about 4-5 shots to the head through a wall with an M4. I suggest the AUG, or, if you have one available, an AK or Krieg. The Scout is generally a poor weapon to use for this, in my opinion. Simply because the reload leaves you completely vulnerable for a short time of roughly 2 seconds. Two seconds of being complete vulnerable? Not for me.
Dealing with Footsnipers
Footsnipers are always going to be in one of three spots. Either side of the ramp, or camping the ledge above BBD. The latter is the most difficult to deal with, because it's almost a guess where the player is on the ledge. Communication is key here.
The Scout has muzzle flash. You can see the muzzle flash from a footsniper on either side of the ramp, even though you can't see the player who shot at you. If you're footsniped, and you didn't see any muzzle flash, the perp is very likely on the ledge above BBD. Tell your team! A bit of walling should get the job done. Help them, and yourself, even more by giving them a likely position on the footsniper. If you're in the very back against the wall, at the corner of the underpass, with the shed in front of you, your footsniper's on the right side of the ledge - a good 8 feet from BBD, but at least 5 feet from the wall. This is where he would have to be in order to have your feet in his field of view.
If you did see muzzle flash on one of the sides, shoot back! You'll need to fire a very tight, accurate pattern to be effective, and you'll need to place your shots through the metal door that only comes halfway down in the front. Look at the ramp angle, and adjust upward along it. Remember, you want to aim for the head to inflict maximum damage, and be sure to remember the ramp levels off after a point, it's not at an incline all the way up. Adjust your aim accordingly for these factors.
If you're confident you hit him, he moved. Adjust quickly and get another couple bullets into him. A footsniper hit through the wall will typically move up the ramp, closer to the front, as moving backward would only place him in your crosshair. So place your last bullets further left if the player is on your left side of the ramp, and further right if he's on your right side. This way, he'll walk into your shots.
Dealing with the Vent as a T
This is the most common form of "walling" a T player will have available to him. What do you need in order to do it effectively? An AK-47, Krieg, or Deagle. A Galil will do the job well, too. You'll need to learn to recognize the sound a player makes on a ladder, and the sound a player makes when he leaps from the roof into the base of the vent. A decent pair of headphones are a big part of using sound anytime you're playing CSS. The last thing you'll need is a pair of functioning eyes, and patience.
When a player uses the vent ladder or jumps in, you'll hear a telltale sound give him away. You will also see the soles of his boots as he crawls through the vent. Don't give him a chance to shoot back! And here's where the patience part comes in. When you're hit with a bullet in CSS, your movement slows down dramatically. A player crawling through the vents who's being sprayed with bullets is almost completely stuck in place. When you're shooting at someone inside, take your time. He's not going anywhere. But the moment you stop to reload, he's off like a racehorse, and in the UV before you've finished reloading your weapon.
Always pay attention to the things going on around you. When I play, I usually take a second before rushing off, move my crosshair over my teammates to see where specific people are going, then move on to my position. When I see a teammate was killed, I check to see who it was. If it was the guy who said he was headin to the vent, then surprise! I know someone's watching the vent, and I'll communicate this with my teammates at the back and front of the warehouse. If I'm then told that the vents appear to be clear? I know a T is camping lower vent! So what do you do? Drop in quickly - don't use the ladder - and prefire him.
So as a T, glance at the vent every once in a while. If the guy covering it is now lying dead on top of the boxes, and there's blood spattered on the wall behind him, you probably have an intruder in your vent. Look for the boots. If you dont see any, he either dropped down, killed your vent guard, and went back out on the roof, or he's in the UV (or possibly already inside the office! o.0) Most experienced players never leave the inside of the building once they're safely inside for more than a matter of seconds. This includes the vent. If I drop into the vent and kill a guy watching it, I'm sure as heck not giving that advantage back to the Ts! I'm movin my rear toward the UV asap.
The CT Box Rush
We've all been playing as a T, took a bit longer to buy our weapons, and found ourselves killed before we took one step. Odds are if this happens to you, you were killed by the CT box-rusher.
The CT box-rush is pretty well known. Basically all there is to pulling it off is making sure your weapon is in your inventory, and a knife is in your hand, when you're released from the pre-round buy period. If you bought an M4 (which is arguably the best weapon for this rush), don't rush the box and equip your silencer at the same time, you can't afford to take that extra time running. They'll know where you're shooting from whether your weapon is silenced or not. =P
So you've got your weapon in your inventory, and a knife in your hand. The round begins. Move quickly, avoid bumping into your teammates, and go to your immediate right, along the truck. As soon as you're out in the open area, turn 45 degrees to your left and run directly to the ladder leaning on the two crates against the warehouse. The idea is to take the shortest route possible. Press 1 to pull out your rifle the moment you hit the ladder, it'll be charged and ready to use by the time you're at the top. Don't go to the roof, just to the top of the first ladder. Line yourself up with the very edge of the crate, move forward until you're against the building, or at least pretty close, so you don't block teammates, crouch, and spray your weapon through the wall. After 15-20 shots, you'll know if you hit someone. A bullet that hits someone through this wall sounds different than a bullet that didn't hit anybody. If you didn't hit anybody, get up and move ASAP. They'll be shooting back in a moment if they haven't started already. If you hit someone, you may want to continue shooting until you register a kill, empty your magazine, or don't hear bullets registering anymore. If you hit someone, but you're being shot at and you've been wounded, you'll need to decide if you want to push your luck for a free kill (that you may not get either way). It's up to you. Just know that a CT can be killed by a T who walls here just as easily, and again, the T here has the advantage, because if bullets are coming out, he not only knows you're there, but he can stand just off to the side of your bullet spray while he shoots back, unwounded. Be careful with this one.
Simple to do. Effective when properly executed. Always risky.
The Bay Door
There are a few risk factors with this one, regardless of which side you're playing. Here's how to do it.
The bay door is the small silver-gray "loading dock" door toward the back (or side alley) part of the warehouse. IMO, the only time it's ever worth your ammo to wall here, is when you know for a fact someone is on the other side, and your crosshair is on the person. How could you possibly know? The radar. The radar works pretty simply. When you or a member of your team sees a member of the opposing team, the member of the opposing team will show up as a red dot on your radar. So let's say you're a CT, and you're standing near BBD, outside, trying to get an angle on someone. Suddenly your radar blips red at the bay door. A scouter on your team probably saw the T standing there from the front. So you know there's a guy there. Now you have two options. Strafe in BBD, prefire kill him, and strafe out? Or go wall him, not exposing yourself to any fire from any angle (except the possibility of being walled in return). I generally choose option two.
If you're a T, you're at the greater risk at this spot. If you're standing there shooting through the door, you have your back to BBD, allowing someone the opportunity for an easy kill. You're blind to the front door, and if someone happens to come inside while you're shooting the door, you'll be easy prey.
I think that's plenty to soak in during one sitting. Practice, practice, practice.
This is just a sort of compilation of tips I've picked up while playing, things people I know taught me, etc. Some of the tips are really basic and won't be of much help to an experienced player, some of them are a bit more advanced. Anyway, hope these help someone. lol
Different weapons have different firing patterns due to different rates of fire and recoil. For example, the AK-47 vs the M4A1. If you're standing up, and spray the rifle, you would want to aim your M4 at a player's neck, and the recoil will raise the rifle (and your crosshairs) into the target's head. With the AK, you could effectively aim at a target's groin, and the high recoil of the AK would raise your crosshair into and past the target's head area very quickly while spraying. Obviously using this tactic isn't the best idea, as a skilled player will just aim for the head right off the bat and fire controlled bursts.
Along the lines of spraying, which contrary to popular belief can be quite effective (when mastered), once you become comfortable with the weapon's recoil and shot pattern, you need to get comfortable with countering that muzzle-rise. In other words, as you're spraying a rifle, you need to drag your mouse downward slowly, so as to counter the muzzle -rise and keep your crosshair on your target (or in the spot where your bullets will land... more on this later).
I see a lot of new players running around, turning corners, with their weapon crosshair pointed in poor directions. Far above where a player might be, far below a player, etc. When you turn a corner, come up over a ladder, cross a threshold on a roof to find a player below, or open a door, move (or stand) with your crosshair pointed where you expect the enemy to be standing. You don't want to see a player, then have to move your crosshair to him, then perfect your aim, then fire. It can all be done in a matter of a second or two, but when you're playing against skilled players, even a split second can be the difference between a kill or a death.
When you're shooting at a player, you're not shooting at the player. You're shooting at his hitbox. A hitbox is simply an invisible area on a player where a shot will register as a hit on the Source engine. CS:S is imperfect, like everything else, and when you see a player, know that his hitbox isn't always exactly where you visually see the player. CS:S hitboxes trail very slightly when a player is moving. Picture a slinky ...slinky-ing down a flight of stairs. (=P) As the slinky descends the stairs, it expands and contracts. In it's starting position, the slinky is still, coiled tightly. This would be a player standing still, or crouching down, not moving. You would want to aim at the bulk of slinky, or the mass of the player, as you shoot. His hitbox is centered within the graphic of the player you see. As the slinky moves downward, it expands, and it's no longer coiled tightly. This would be a player running across a walkway in front of you or jumping down off a small building. In this situation, you wouldn't want to point your rifle directly on the graphic of the player. While you may have aimed perfect on the player's head, and placed a shot or two exactly where the graphic for his head is, you'll have missed your shot, because his hitbox is actually slightly behind the graphic of his character. Picturing the slinky, you'll want to aim slightly on the tail-end when the slinky is expanded. In other words, you'll want to aim slightly behind the player when he's moving, rather than directly on him. I know this sounds crazy, but with some practice, you'll see that this is true. =)
Earlier I mentioned pointing your crosshair so your bullets will land where you want them to, rather than where your crosshair actually is. Like I said, every weapon has unique firing patterns. I honestly don't have an accurate description of how each weapon works, but I do know how the deagle works. If you're spraying with a deagle, you only have 7 shots, so you want to make sure they hit. At the same time, you only need one headshot to kill a player, even if he has a helmet. When spraying with the deagle, you want to hold your crosshair slightly down and to the left of the spot you want to hit. So if you're spraying a deagle at a guy standing still and you want to hit him in the head, try aiming at his right shoulder, or even his right bicep area, at medium range. Practice the shot patterns with different weapons on walls. Find a small crack, or use a custom spray on a wall, then back up to medium range, and fire away. It's a great way to learn how each weapon fires.
A lot of players seem baffled when they're killed through walls, and jump at the chance to call "wallhacks" on a person. Other than the obvious spots on maps where spraying will usually score a kill or two (outside boxes to office ramp on assault), there are things people do to give themselves away.
Flashlights. For the love of God, don't stand by a wall and beam your flashlight on it. It's the easiest target from the outside that just screams, "Hey, I'm right here. Standing nice and still for you. Kill me please..."
Rifles with muzzle-flash (all of them except the M4 with the silencer equipped). Same thing as a flashlight. The muzzle-flash is very obvious on the other side of the wall, and lets people know you're standing right there.
Familiar with the term "clipping?" Clipping is present in CSS. Essentially, clipping is when a part of a player, usually an arm or weapon, can "pierce" a wall and appear on the other side. I'm using examples from cs_assault, because that's the primary map I play, but there are spots on most maps where clipping is present. In assault, your weapon and arm can clip through every single outer wall of the warehouse. If you're standing flush against a wall and looking right at the wall itself, yep, your weapon is visible on the other side - again, a big target for players on the other side to shoot at.
No flashlight, no muzzle flash, no clipping, walled anyway? Let's make some noise.
Sound is an incredibly important part of CS:S. The sound of footsteps on a catwalk, a player jumping onto a cardboard box, a player jumping from a roof down into a vent, the general spray of weapons, the realization that some weapons are only available to one team or the other, they can all give you away. Learn to recognize a weapon by the sound of it being fired, and react based on whether that weapon is probably being fired by a T or CT. Valve made this easier by incorporating the radar in CSS. Use it, for your team's sake, as well as your own. Learn to recognize common sounds like footsteps, and don't be afraid to shoot at a wall when you do hear an enemy on the other side of it (unless a server has a rule against this... which is ridiculously common). Eventually you'll be able to pinpoint an enemy on other sides of walls, and through that, you'll be able to kill an opponent without exposing yourself to enemy fire - the ideal situation.
Learn how to use angles when throwing nades or flashbangs, learn their blast radius, learn how long an enemy is disoriented for before the flashbang effect wears off. Use flashbangs and smoke to your advantage, but know that at certain times, they'll be more detrimental than helpful. Recognize the pros and cons of each and when they're best used.
This last point is probably the biggest mistake I see people make. Let there be no doubt in your mind that a player with 1 HP is still very deadly, whereas a dead player won't be shooting at you.
Don't make the mistake of shooting at an enemy before you can kill him. If you turn a corner and a door is open, do NOT shoot the door, unless you're completely certain he's there, and you have the means to score a headshot (IE, if the player is clipping the door). Even if you hit the player, odds are you won't kill him unless he's almost dead, because every weapon in CSS takes a huge damage loss when penetrating walls. Instead of shooting through the door or wall when you know an enemy is there, it might be more better if you take some cover and wait. More often than not, if a player opens a door, he plans to enter or exit through that door. Be mindful that he may throw a flashbang, so be ready to avoid the disorienting effect (this is as simple as turning away, or placing something between you and the flashbang), and be ready with your crosshair pointed where he'll be. In this way, you can kill the player, taking him out of the match, rather than injuring him, and allowing him another opportunity to kill you or your teammates at a later time.
The most important thing is to always learn from your mistakes, and to never make the same mistake twice. Watch your team, as well as your opponents, and learn from their mistakes, so you don't make the same one later. Good luck. =)