Boomers, do not spawn behind(!!), always ahead, you'll just end up chasing the survivors forever.

Arc your bile so it travels further or puke from unexpected places. You can even arc it over objects between you and the survivors (like half walls or bookcases) and safely boom them without them even seeing you.

Set yourself on fire so you can control your suicide boom by dropping into them (surprise!), puke on downed people to make sure they die, puke on people trying to crown witches to make them fail.

See someone standing near an edge? Get right up in their face, if they pop you they will probably fall off the edge, or out that window for an incap!

Use your "ghost" form before you spawn to help speed up reaching the survivors by running at them from a ledge (or roof etc) and as you run off the edge, spawn! Time it carefully though, you can't spawn if you're jumping.

If you "pop", you can break a smoker's grasp on a survivor (could be bad if they aren't incapped yet or could be good if you have 2 infected teammates down on a spawn timer but only 1 survivor still not incapped), you can free a charger and instantly refill their charge bar (see previous scenarios on how it could be good or bad), and knock a jockey or hunter clear off their prey. Be aware of this when you get close to survivors in "bad situations". You don't want to be "that guy" who screws over what could have been a game winning moment (and on the other side of the coin, using this to your advantage could create opportunity where none existed before).

If you've already "blown your load" (successfully or not), you can sometimes get a panicy player to kill you next to or ontop of a survivor who hadn't been boomed by your first attempt. I can't begin to count how many times I've failed a boom but then redeemed myself with a 3-4 man death-pop.

Chargers you -can- hit them all if you have a nice spitter to lay out some dmg. ESPECIALLY if they are by a railing. Charge-bounce by a railing into water or long drops = death.

Always charge AWAY from the goal (back towards the safe room) don't give them extra free points; Make them lose ground stopping you, not gain it.

Be careful not to charge too close to a survivor. Much like a hunter being dead-stopped (punched in the face before the pounce connects), a charger can be dead stopped by starting the attack when they are all-up-ons. You need a bit of distance in order for the game to not bug and actually register that you grabbed them.

Coordinate with your spitters for great dmg, or coordinate with your jockeys and smokers if you don't feel confident getting that "death charge". They can hold a victim in place for you so you don't have to feel rushed getting them out that first window on Dead Center (for example).

See some stairs leading down? Charge them from the top of it and they usually take bonus fall dmg! Aim for ledges, windows, make them fly off the roof, aim for death!

See a survivor at low health? Your punch does 10 dmg each swing. If you use your time wisely you could punch the low health survivor down and then charge the person who tries to come rescue them! If you can incap someone, do it, even if it means you don't get the glory of a charge slam.

Always remember survivors standing up from something that knocked them down (a hunter pounce, a bounce from your charge, etc) have a moment of immunity to your charge and you won't be able to grab them. Plan accordingly.

You take more dmg if you're shot in the head, so if you're going in to punch a survivor try moving erraticly or jumping up and down in order to make it harder on them.

Spitters, don't waste your spit on a bloody hallway; spit on someone hunted, charged, hell even a down person being picked up is more useful than "spit in a hallway! they can't dodge it." (Cause backwards is hard. >_>;;).
The exception to this rule is if you've already recharged and you're the last man standing. If you're not worried about possibly losing the spitter for the next volley of spawns (by instead choosing to hide or get back into ghost-form), feel free to hallway-stall, you could get lucky and a survivor could bathe in it.

Scratch the person being picked up and it interupts the pick-up and they have to start over!

Spit on the elevator door threshhold near the end of the first map of Dead Center, it will spread really far and then run in there and stand in the corner that they are all huddled in and scratch! Either you get free dmg or they'll shoot you and that free corner is suddenly burning yellow. This holds true for most elevators and a couple of door threshholds as well.

Spit has a slight homing to it, so if you need to hit a survivor super far away, point towards them then aim in a very very high arc (we're talking looking at the sky high); the spit will drop down on the first survivor it passes over in a sharp descent allowing you to hit survivors you can't actually see. The homing doesn't work if you're too close to them, so this is more like a "hail mary" spit.

Spit also bounces off walls, so if you don't want to expose yourself to someone coming around a bend or in a room around the corner from you, aim for a nearby wall in that room, it will bounce off the wall and hit the floor like a ball would and spread from the point of floor impact. Lets you spit without being seen! This also works for ceilings if you need to spit over something like a bookcase in Dead Center mall. This may just be me but it seems like spit that gets a bounce (off a wall or ceiling) tends to spread wider than a normal floor-spit.

Don't spit exactly on survivors, your spit will spread. It's better to spit infront of a survivor in a corner (for example) that way it not only gets them, but you don't lose any of the possible width your spit could have spread to by sticking it in such a tight spot. The graphic for the spit is also not entirely accurate and even if a corner looks clear of spit, it may infact be polluted.

Jockey, don't listen to some people (kooky); you are far from useless. When a charge comes in, grab the one furthest from the charge and run that survivor in the opposite direction, take as many turns as you can, hug corners, make it hard for them to snipe you.

Try and keep something between you/your prey and the rest of the survivors.. bookcases, pillars, walls, corners, anything that works! Bugs Bunny that ♥♥♥♥ and watch the dmg rack up.

Scratch downed survivors being picked up and delay for the rest of the infected to get there or spawn!

You see a ledge? Grats you are now a charger, run those bastards right off or you can take them out a window. Bonus: if you do bring a survivor off a ledge, your pounce will actually recharge faster! Kill their rescuer!

Got a wobbly charger on your team? Hold a survivor near a window or ledge and let them death charge! Elevator shaft? Incap or death!

Did you know you can double jump to get to a survivor faster? Try using your jump button (space) and your jump attack (left click) after each other. If you do the jump attack first, then even if you're only using your normal jump and land on a survivor it will count as a pounce and you'll start your ride.

Hunters, you get extra dmg if you pounce from a far enough distance, usually accomplished from somewhere high and dropping down on your victim.

You're silent if you don't crouch, so follow them if you spawn early (or reposition) through normal walking and only crouch when needed. Ready before you even spawned? Crouch before you spawn so you're ready to pounce immediately.

Get knocked off? Crouch immediately and jump away, or jump on someone else! If you can manage to pounce someone ONTOP of someone already downed, you do dmg to BOTH of them..

Aim for spit, or scratch the witch to make her pissed, then after she goes after someone, pounce the one the witch is wailing on to kill them faster (and the witch's dmg adds to your own for close dmg tie games!)

See someone boomed? Pounce them and they can't clear the horde off of them.

What not to do as a hunter: jump into the middle of the survivors, alone. You'll get picked off very very quickly. Don't be that guy.

See someone smoked near a ledge? pounce them! They could fly off the ledge and die and you will free up the smoker to pull the one trying to rescue the one you're on (but make sure it's okay with your smoker! Otherwise this could be taken as bad manners, and of course, pounce a different target if 2 people are already downed..).

See more than one person near a ledge and grouped up tightly? Pounce one of them and the other will stumble, if you're good (or lucky) they may stumble right off the edge and you'll get a double incap.

If you can be lit on fire by a molotov, incendiary ammo or a gas can having been shot, you will do extra damage on your pounce. Be warned, you get no extra damage if you've been lit on fire by the environment! (the damage dealt was reduced in the March 11 update but still works )

Know those survivors who have no idea what's going on around them? Those are the people you never crouch around and instead walk up and scratch them from behind or hide in a horde. You do 6 dmg per swing, so kitty-scratch away and then flee when they become aware, or pounce but remember there's a 1 second charge timer on that.

Smokers, pull them down from ledges, pull them out from windows. Pull them as they cross gaps (like boards and planks). If they're on a roof, pull them off of it! You can smoke people out of mid air (like jumping across a gap), and if you time it right, they'll take bonus fall dmg.

If you manage to yank one off an edge, duck back out of sight and watch their glows. If you recharge fast enough, get back out there and pull the rescuer right down next to your last victim.

Hold them still for a charger to get a death charge. Some of those death charge locations you can also pull them at just the right angle so they dangle over the deadly spot and when someone kills you or shoots your tongue, they'll drop to their death.

Pull them into spit, or pull them into "just the right position" for the rest of your team to coordinate something else like trapping them for a tank.

Grab that straggler at the end, grab that rusher at the front, or grab the one who comes to rescue the rusher or straggler who has been jockied or hunted or charged.

Drop them into fire (your tongue will catch on fire and break on it's own, they'll take fall dmg and fire dmg!), and just be an overall hinderance and incap machine!

Tank, don't go in if they're all green, they'll probably just juke you (run around and kill you without you doing dmg). Coordinate with your team! Throw rocks from a distance while you wait for your team to whittle them down from green health to a much more friendly yellowish-orange.

Aim your rocks high! They too arc and will travel further that way.

See anyone near an edge? Smack them right off of it. Running up stairs to a roof? Aim that way and smack, watch them get air and maybe even die!

Scare them into position for death charges!

Want to throw a rock quicker than usual? Try jumping into position (from a ledge or roof) or in place while you throw your rock, you will move towards the survivor while the animation goes through and they won't have as much dodge time.

Bring cars, bring luggage carts, bring forklifts, bring it all!! Everything you can hit will be instant incap if you can manage to smack one of them with it!

Use tab to find out which survivors have molitovs so you know who to avoid (and who your teammates should be aiming to incap first!).

On fire? If there's water nearby get to it fast and put yourself out!

See a survivor in water? They move slow, you don't. Get that bastard even if he's full green health!

See someone on a ladder? Try and avoid climbing if you can, you go extremely slow!

Close enough to punch? Why not try the one-two combo? Click both your left click and your right click at the same time, you'll punch the survivor and start throwing a rock, the timing should be just perfect that as they are getting up from the punch, your rock smacks them in the face!

You won't lose control of the tank if the survivors are in the safe room. If they aren't and you're worried about losing control (or passing it to another survivor), but you've managed to incap someone, you can always try and be ninja near by and when your control-bar is getting low, run over and smack the downed survivor for a reset.

Overall tips -

Coordinate with your team (duh). Go all at once, even if you think you're going to die. If everyone else has spawned, so should you. Stay as close to on the same spawn-timer to each other as you can. More hits, more often, and more chaos = more dmg!

Grabbers (Anything but spitter, boomer, and tank), keep an eye on survivors when they are leaving "points of no return" (ex: the hole in the tunnel of love they drop down, hole they drop down in the sewers of no mercy before heading up to the hospital entrance, the ramp into the mill on hard rain, etc) and grab the last one down. If you coordinate with another grabber you can even take down the last two (who think they are safe in a pair bwuaha).

Jockey or charge from the top of manholes (the ladders leading up to the street levels) and they'll take fall dmg when they hit the ground. Spitters can stand above it and block them from going up (same with hunters) and spit down the hole for those incapped there or standing near/on ladder. That will trap them on the ladder! You can hunter pounce down holes but they don't always give you bonus fall dmg.

If you have a spitter, coordinate with your chargers, hunters and smokers (even jockeys if need be). Spitters stay back and watch the action, then spit on the ones in trouble. Only time you should be spitting on nothing but floor is when everyone else on the team failed and you need to stall the survivors from pushing forward. Even then, you can always try and save the spitter for the next wave of attacks. Better to be up and ready to go when they are, then to get killed off sync and they have to wait the extra 10 seconds to re-sync back up.

If you're a jockey, coordinate with smokers and chargers. Grab stragglers, grab runners, and always go in the opposite direction of the chaos!

If you're a hunter, watch the action start off, and swoop in at the worst possible time for the survivors.

If you're a charger, you're the opening act usually, coordinate with your boomer (the other usual opener) and see if they would rather go first or take advantage of the chaos. Tell people where you're going to charge, tell your spitter especially so they can be in position to spawn and spit on your slams.

Boomers, get into position early and spawn at the VERY last second. Start puking before they round the corner (or finish moving into position) then you can usually get the puke off without someone stopping you with a push. Coordinate with your chargers, and if things are going well and you're late to the party, puke on downed people so they'll possibly die (and be hard to pick up from all the hits resetting them).

This seems common sense to me, but I figured might as well throw it in there: Use your ability to get back into "ghost" (or spawn) mode by running away from the survivors. If you survive and the rest of your team doesn't, either waste your life right there so you're on sync with them, or run away from the survivors so you can respawn at a different point and not get shot trying to chase them clear across the map. Remember, you won't get the "You are too far from the survivors" prompt that allows you to re-ghost if you run FORWARD on the map; You only get it if you run back towards the safe room they originally left.

Any S.I. can take advantage of the witch. Be careful though if you scratch her, you are dealing damage and can make her easier to kill. On the other hand, ducking behind her (especially as a hunter or jockey) can make an unaware survivor shoot the "hunter" they hear without realizing the sound they are aiming for is lined up with a deadly witch. Smoke-pulling a survivor into the witch is another tactic which works well when the survivors are distracted (with, say, a horde).

If a survivor is under attack by one of your teammates and you're recovering (or don't want to steal their kill) you can still help! If you're a jockey or a spitter, and a survivor is smoked, duck down and claw at their feet. You'll add on some dmg but make sure you duck, you don't want to break the tongue. Same goes for someone being jockeyed. While your spit recharges, duck down and scratch to help your jockey friend out.

If your Boomer friend has managed to cover 3 out of the 4 survivors and you have an incap-class-special-infected, aim for the one who is clean. The other 3 will not be as quick or accurate as the one who can see clearly and if you're lucky the response time will be so slow you can sneak an incap in!