HELP

As a smoker, I tend to pull the guy that is behind everybody, so they have to catch up to him. Be well hidden also. For a spitter, spit your acid by a door they MUST pass through in order to continue, it stalls them, and gives a chance for your team to attack, and for you also.

Well the smoker you just need to find a good vantage point like a sniper, and just drag in survivors from roof tops. And have your team beat him. The spitter is kind of like the smoker without he tongue , just find some vatage points, like small hallways or at cliffs, just make sure to stay to the shadows.

I can't say that much but if you go to (or search) left 4 dead smoker tips and tricks. Look for one by Criken2 and there is another one there called Left 4 Dead 2: Versus Gameplay New Infected Tips and Tricks which includs the spitter. Hope this helps (and it's on youtube).

for the spitter, its really good to spit on a downed survivor when they are being picked up. also, try to spit on a survivor who has been pounced by a hunter or charged by a charger. if the only spit on a pulled survivor when they arent moving(i.e something is blocking them from being dragged further, or they are pulled to the smoker). when a survivor is jockeyed, spit near the jockey so he can run the enemy into the spit. the spitter can deal a lot of damamge, but it relies much on timing and accuracy.

i understand your trouble with the smoker. a huge help to the smoker is a somewhat-open field and a freshly boomed enemy team. the boomer is a huge asset to the smoker. when he booms, pull either someone who hasn't been boomed on, or, if the whole team was boomed, pull whichever one backwards. this works most of the time because when a team is boomed, the outline of their teammates goes away and wont come back for like 20-25 seconds. also, try to pull people off ledges. this can stall the team for a decent amount of time so that your teammates can cause damage. another thing you can do is when a jockey is riding someone back, you can pull the person thats going to save his/her teammate. this can be used for hunters too. a hunter pounces someone, you pull the "savior", the hunter gets more damage in before dying. same thing with a charger. a funny thing you can do is pull someone toward a witch. when you hear her, find a place you can spawn behind her. when a survivor gets close enough for you to pull, pull him. i picture this in my head as two things happening:
(1) the pulled survivor startles the witch, he cant move, she downs and/or kills him.
(2) someone tries to shoot you as you're pulling but before (1) is completed, and THEY startle the witch instead.
thats all i have for now.

also note that when spitting longer distances, aim the crosshair thingy higher. it doesnt go straight at the enemy until it hits them. when spitting longer distances it flys in the air and then curves down, so sometimes it wont reach the survivor(s). this works well when your hidden but on level grounds with the survivors.