Always watch were your team mates are and learn to be aware of the available environmental benefits. If you get covered in boomer bile get yourself quickly into the nearest choke point. A room with only one door means that your team can protect you easily from the attracted horde. Corners work just as well when no room is handy, your team can get next to you and help keep the horde away from you. Another great choke point for use in this way are hallways or train cars, the horde and Special infected can only get at you from two sides in these points and that gives you an advantage.

Be aware however that at some points in some maps when playing with certain groups of people it can be considered cheating to use environmental factors such as one entrance rooms. An example of this is the closet next to the elevator in the no mercy movie.

When you go to use explosive or Molotov's make sure that they are not being wasted, it is pointless to use one of these items for only a couple of infected save it for when you need to deal with large numbers. As well as the explosives you can pick up there are other ones that are part of the environment. These are gas bottles, gas can's and oxygen cylinders. All of these can be place strategically and used to great effect against the infected. Look for these as you make your way towards the end of the map. Use of these at choke points can effetely eliminate any threat from the horde and allow you to move on more quickly which helps to ensure that you survive to the end.

Melee is a great weapon when dealing with the horde; however the player base seems divided about wether it is good or bad form to constantly melee as you run through the level. It seems to depend entirely on the people you are playing with at the time.

In Left 4 Dead height can be an advantage but it can also be a great danger to a survivor, remember at all times that the infected can climb, and if you hop onto a car roof you are exposing yourself to 360 degree attacks which can prove rather unhealthy for you. Using an elevated position with something solid to your back however can give you a tactical advantage for a time and shouldn't be discounted as a great place to be.

Be absolutely sure however that you are not staying up on a spot that has a one way drop when your team mates jump down. If it is then you are simply making yourself an easy meal for any passing hunters or smokers. The only way to avoid this is to learn the maps that are used for versus mode.

Boomers

As a boomer your one job is to get closes enough to cover the survivors with bile, a good boomer is the key for the infected to do well against the survivors. When a survivor is covered in bile they are partially blind making it far easier for other Special infected to successfully attack. The bile also attacks large numbers of the common infected adding numbers to the issue.

When playing the boomer you have to adjust to being very slow, easily spotted due to the large size, and a very very low health. Spawning far from the survivors is generally a bad idea and will normally result in you being shot without covering any one in bile.

The closer you can be before you spawn the less time the belching sounds the boomer makes have to give you away. Spawn close and use cover to hide you from the survivors. Covering survivors with bile while they are in a choke point will cut down the effectiveness of the horde you attract. Ideally you want to hit them when they are in area's were the common infected can get at them.

When playing the boomer it is highly advantages to remember that you can use height to your advantage. Spawn on top of buildings and jump onto the survivors when they are underneath you.  If you can cover all four survivors with bile then the rest of your team has a good chance of getting in and doing decent damage.

I differ from other with regards to what a boomer should do once they have covered the survivors with bile. If there are hunters pouncing the survivors you have just vomited on then it is imperative that as a boomer you get distance between you and them. If you explode next to a hunter who is on a survivor or a survivor that has been caught by the smoker you're death will set the survivors free.  Try and get to spot where you can wait for your primary attack to recharge. If the rest of your team hasn't shown up then it can be advantages to get in close and claw at the survivors. Many people will be distracted and won't shoot you right away. This allows you to get some extra damage in before they other infected arrive.

Being a boomer can be a lot of fun, however you need the rest of the Special infected to get much damage done. So when you are ready to spawn see if the rest of your team is ready to spawn, if they aren't, wait for a time when they can spawn and attack just after you have attacked the survivors.

As always there are exceptions to any sort of rules. Boomers can be very effective in slowing a team of survivors down to allow the other special infected more time to re-spawn.

It is highly possible as a boomer to assist the other special infected in thoughtful ways. If you have your primary attack charge and a smoker grabs a survivor, it is better to spew on the single capture survivor than to run off looking for the rest of them. By covering the lone guy in bile you attract a horde to do a lot of extra damage to that one person while the smoker does damage and keeps them helpless. This can very quickly incapacitate a player. Once you have spewed on the poor guy then run off looking for the other team mates. Even wit out your primary attack if you can get close and be killed you will still cover the rest of the team in bile and will then put a large obstacle in the way of them saving their team mates. I know the score at the end is very attractive to be on the top of, but the game is all about teams and sometimes the guy with the most damage didn't do the most critical work.

The same tactic should be used for hunters who pin a survivor, by covering the pinned guy in bile you not only accelerate his demise but in this instance you also add a human shield of infected to the hunter, this can allow him to get anything from a few extra hits in, through to a whole heap of extra hits in. Depending on the team you are playing.

There can be a tactical advantage from spawning behind or close to the end of a team and covering the last survivor in bile but this tactic only really works at some points on some maps. For most of the time and against a lot of players a boomer who spawns behind or goes after the last guy is a boomer looking to upset their own team mates and to a do very little damage all up. Lone survivors are easy takeaway for smokers or hunters, leave them to your team mates they will mop up a single survivor in no time especially if you can cover the rest of the team in bile and keep them from going back to help the last man.

One last trick that can be done as a boomer is very difficult to pull off but can be done with some thought and a whole lot of luck. Just as your death can cause hunters to be knocked of survivors they have pinned so your death can also be used to knock survivors off of ledges roofs r any other high point on the map. You need them to be close to the edge blinded by your bile is very helpful when attempting this. Then get very close to them and claw at them if you are lucky they will kill you while trying to kill the horde that you have brought down on them. If all goes well one of the survivors will suddenly find himself hanging onto an edge needing he help of a team mate to get out of this predicament. But as a boomer you have just increased the chance of your team winning as it is now 3 vs 3 and all three of your team mates have the ability to incapacitate a survivor.

Smoker

When playing as the smoker there are certain natural obstacles you need to learn to overcome. These being that you are slow, snails are probably slightly faster when it comes to running than you will be. You have horrible cough you just can't seem to get rid of ever and every damn survivor for miles around can hear you. And on top of all of that you mutated with a visible cloud of smoke constantly around you so you can be tracked and seen from a distance. These obstacles make playing the smoker very different from the other's, you require patience and stealth, I know what I said about easily seen and heard but the smoker is a ranged attacker. Waiting patiently behind a wall and snaring a survivor through a wall or from a roof top can help to keep you safe and still hurt the survivors.

Smokes are not a frontal assault species and attempting to run in and get some damage dealt will result in massive damage being done to you and that's about it. You need to look to the environment for help.

Smokers can be very deadly when they wait on top of or a fair distance behind the survivors and attack once a hunter or a boomer has attacked. Then you can snare yourself a tasty morsel of food and drag it all the way back to eat. A good drag can make the survivors have to reverse their direction and come quite a distance back to try and save their team mate. This leaves them wide open to attack from the horde as well as from hunters.

Another great place for smokers is up high or sometimes even down below were the survivors are. Grabbing that last man in the line as the rest run down a different alleyway can lead to instant mayhem. And by doing it from a nice protected spot on a roof means that you get extra time to deal out damage as the team mates of the snared survivor must get close enough to melee him to set him free.

Smokers can also be very nasty opponents when they use one way drop offs to snare the last person to go through the drop off. This leaves you with a helpless victim and the rest of the survivors can't get back to help so the poor guy you have gets left 4 dead.

There are several points in maps when as a  smoker if you snare a victim and drag them off the ledge you do extra damage and quite often force the team to be stuck waiting for their team mate to retrace their steps to get back to the rest of the team. This adds valuable time for the rest of the infected to do even more damage to the survivors. In a really good situation the one team member you dragged off will end up being incapacitated and another will have to come down to save them. This gets you a split team and can be very easy pickings for the infected.

You are also a great weapon in helping hunters with eliminating the survivors. IF a hunter has a survivor pounced and you can snare the next survivor to come along to help you increaser the damage dealt to the survivors while giving the hunter more time to do extra damage. Never underestimate how beneficial this is to the overall team's performance.

Hunters

Last but not least with come to the fashionable hunters. You are of normal build, you have a little more health than the other Special infected. Your primary attack is the pounce which you can use to quickly cover large distances or use it to get to great heights. However every time you leap you let out a wailing scream alerting everybody around that you are there and that you are leaping. When crouched to prepare for your primary attack hunters begin to growl alerting anybody close by that there is a hunter close.

When playing as a hunter you need to remain focused and not bouncing off walls and doing back flips in the air just because you can. The team needs you to be prepared to pounce lost survivors. A survivor that separates from the rest of the team should be an immediate target for your claws.

If the team is one that stays together, then wait for the boomer to attack and once they have go after an survivors not covered in bile as they are the greatest threats. If all survivors are covered in bile then the choice comes down to personal taste. Just grab whichever one looks yummy and pounce away.

As a hunter you can replicate some of the smoker tactics. Finding the last survivor to go through a one way drop and pouncing them, will defantly cause them to be left 4 dead? This can cripple a team when done right. With a smoker and a hunter it is possible to use this tactic and eliminate half the team on the spot.

You can also be of great assistance to the boomer, with the ability to leap you can leap in close to survivors then leap away distracting them long enough for the boomer to get close and cover the lot of them in bile. This lets you leap back and pounce a nice tasty survivor with far less chance of being hunter punted.

One last trick for the hunters is to use the very weapons of the survivors against themselves. A hunter on fire while they may be dyeing slowly from burning alive. You are not a crispy critter yet.  Pouncing a survivor while you are a living candle deals out extra damage to the survivor for the time you are on them.

Tank

This is the Special Special infected that you get to play at certain times during a map sometimes. When you are the tank the rules are basic and simple. You must attack failure to attack will cause you to lose control. Hit and hit some more is the tanks motto. They have no quite method everyone knows your there, and so you have to attack. As the tank you should do you're very best to avoid being set on fire. Once on fire you only have 30 seconds at most to live. You are not the fastest guy on the field however so try to avoid chasing a green survivor around they are quicker than you and can stay outside of your reach. Look to go after the guys who are already wounded, they are slower and you can chase them down and smash them around. While the tank is the biggest of the Special infected if the other infected don't help you it can make your life hell.

Look for objects outlined in red; if they are outlined in red you can punch them at survivors. This includes things such as cars, and forklifts. A hit from one of these flying footballs will incapacitate a survivor no matter what their health was. If these items aren't handy a tank can use its secondary attack were you through chunks of the ground at survivors in order to knock the survivors around and slow them down. A good tank with some help can very quickly incapacitate a whole team thus winning the match for your side.

We recommend the following links for further reading in regards to playing Left 4 Dead

Gameplay

left 4 dead wiki tactics

Begginers guide

Infected guide for beginners