Equipment for mid to close range fighting:
AK-47 for the main gun, the power/fire rate/clip size are really good because it only takes 1-2 hits and the zombie is down, and the rate of fire isn't so fast you waist ammo on him as he's falling. But as a backup I go for ANY shotgun or just stick to my secondary.
Secondary is a tie between the Desert Eagle and the katana/macheti/axe(in that order) because cutting down zombies is fun, but that DE is like a small cannon, you just have to treat it like a rifle instead of "pew-pewing" away at the horde. Backup:dual pistols, the rest of the melee weapons just feel slow or underpowered like you aren't really connecting
Molotov is nice but if you have friends I've found that a good plan is to chuck a bile so the horde swarms something then follow it with a molotov, cleans up big rooms real quick(why is it the bile in a jar will attract hordes no matter where it lands but the fresh kind wont?)
First Aid Kit because if some one is dead you are typicaly better off finishing out the round or makeing sure you stay alive till it calms down a bit so you can go find a shock kit. Also if some one has died chances are it's becuase they weren't following the plan.
Pills... I guess, I really don't have a prefrence. The addrenalen is nice but it just doesn't seem to do much for me, and the pills last longer. I'd use the addrenalen if it gave you like a +100 buff on health and you run noticably faster.
Good tactics:
Tank: Spread out, if you group up he will probly run in and kill you all in one go. Keep him running in circles.
Horde/Unusual: Stay close, following a diamond pattern(one covering the front, one to each side and the last guy on bakcup to help keep everthing in check/covering the rear(this guy will probly get a few team hits).) and WATCH EVERYONES BACK and don't worry about your own. This way you don't have to keep spinning around to try and cover yourself leaving gaps in your gaurd.
Special: Watch every one's back. This way if some one gets grabbed by a jocky/smoker he wont get far before your friend is realeased so you don't have to chase after him and get sloppy. Keep your ears open. If you hear any special and don't know where it is or you can't get to it, let your group know cause they may see it/kill it. Don't break formation(diamond or some other prefered). If they split you up they will try and keep you that way, and then your gaurd will have massive holes in it and you will probly die if you don't get back together fast.
Side note: When a charger shows up focus fire. You need that thing dead before he sends people flying/carries someone off. Also he tends to glitch into people he is going to carry off, and there is little you can do about it except make sure he dies first.
Other members:
Front Man: Auto-Shotgun/High-Powered Machinegun, Melee weapon of choice(chainsaw is good) and a pipe bomb to help take off the heat.
Side Guards: High-Powered/large mag Machineguns/Large Mag Shotgun, dual pistols/Desert Eagle(no pew pew), doesn't matter aslong as they dont both have bile.
Rear Guard: Sniper(military)/grenade launcher (this way he wont Tk...as much), doesn't really matter though I would advise against melee as they don't work well at long range(duh), Carry the explosive/incendiary rounds or bile which should be aimed at special zombies.
Sidenote: Mix up the health packs/shock paddles because you don't know who will need what. I would stick with mostly pills because the adr. doesn't do enough extra. Never carry a gun that's out of ammo, trade it for ANYTHING. Always leave a few rounds in the gun if you switch to a secondary so you have something to come back to.
There you go E.A.O.'s guid to surviving l4d2(results not garentied, spelling/grammar errors on purpose)