Though some things are merely touched on, I expect that most players have a subconscious understanding of some of the points I will make. What you should then take away from the things which you may already know is a heightened sense of importance of how each of these things effect the success of your team. Also, though I do not talk about every special infected character, those I do speak of are revered particularly for their abilities, and shouldn't be taken lightly when you next use them in the game.
What elements do we need to take the survivors down? I could put it down to the following:
With the key element of surprise, comes the unexpected attack. The ability to incapacitate the enemy without the capacity to defend against it. This is perhaps the key to initiating the downfall of another team.
So what surprises the survivors?
Being unable to anticipate where the attack will come from.
Now this itself pulls out a few things which aid directly to being unable to predict an attack, and that could be summed up as being Out of sight, Out of sound and Out of the blue.
Spawn at the last moment, keeping your audible presence a mystery right up until execution
- Keep yourself hidden, and come from angles which do not give sight of yourself
When you have the attack under way, the next objective is to expunge their ability to fight and defend themselves. Thus we have next in my most important element of taking the enemy down attributable to retardation.
What retards the survivors?
The boomer is the standard-bearer of retardation. His ability to cover the survivors in bile which effects their ability to see (which also initiates confusion), makes it more difficult for the survivors to cover each other and themselves. But not only this – the ensuing horde has the potential to completely surround the survivors, both damaging them and keeping them slowed. Simply put, played well, this is one of the most effective initiators of defeat for the enemy team.
The downside to the boomer is his fragility- and this means that the boomer has to use the element of surprise perfectly to be able to effect each member of the survivors with his bile. He is therefore best in a lot of scenarios to be used immediately after the first wave of attack has occurred.
The charger, when used at the optimum, will knock down the survivors whilst at the same time incapacitating one member of the team. When doubled up with a boomer, the charger is the natural escort, able to incapacitate the survivors long enough for the boomer to deliver.
The other important aspect of the charger is his ability to separate the survivors, but we haven't got to that yet.
The other infected do not come under this category as they either incapacitate the survivors completely (Hunter, Jockey, Smoker), or they only have a minor ability to cause a nuisance conducive to retardation (Spitter) by laying down the spit. The spitter is uniquely a support damage character, which must be used in tandem with the initiators of the attack. That said, the spitter is one of the most useful infected characters to cause damage whilst the survivors are rendered immobile by the boomer's common infected or being bowled into a tight spot by the charger, unable to escape quickly.
The three key characters to separating the survivors are the Charger, the Smoker and the Jockey. Each type, when used properly, helps spread the survivors out while other members of the survivors have their attentions occupied – an important aspect to the success of separating the survivors.
High damage-over-time characters like the Hunter rank up on many peoples priorities to being dismantled from their friends. This great distraction can cause people to take the initiative to try to save their buddy, and when they do – the characters who are capable of separating them come into their own.
The greater the distance that can be made between the survivors, the farther back you can force them to backtrack, the longer it takes them to move on, and the more time you have to initiate another dreadful attack with the intention of completely incapacitating the enemy team.
Though this itself could be swapped in at any point into the sequence of what is most important, it certainly helps to be confused at a critical point when the survivors are at their peak of fragility. Being able to mix up the priorities of the survivors and delay them long enough for the infected to do their job is part and parcel to breaking them down. This could be the successful jockey who comes back to harass the pick up, the spitter who delivers the second accurate globule onto the survivors or the flying hunter who took the attention of the survivors whilst the real attack is about to occur.
What other factors come into play?
Let's think about this. There exist environmental soft spots in this game where the survivors are particularly susceptible to taking damage. This is different to saying that there are areas where they are susceptible to 'attack', because you can attack anyone, anywhere, and may succeed - but it's how long you can hold it, which is important.
Soft spots come and go, and they can be missed if we deliver an attack too soon prior to one that the highest chances of incapacitating the survivors is taken away. We therefore should strive to find out where these places will be. That said, any location which will likely allow for the elements of surprise, retardation, separation and confusion of the survivors will be candidate for the next attack.
Generally speaking, it is best to time the attacks which cater for the unique abilities of the special infected as a whole. The soft spots change depending on what characters you have to work with. A stairwell is a soft spot for the spitter, as it is enclosed and narrow and difficult to escape from, but will never be the soft spot for a boomer, which render the horde he attracts to be fended from in a tight radius. The boomer would therefore be best deployed in an area which maximises the number of directions the common infected will come from. When both the boomer and a spitter are on roll, and the soft spots are close, you must weigh up which area is most likely to be the easiest to initiate the most devastating attack.
Coming together and initiating great attacks requires collaboration between the 4 players. Each player makes up 25% of the team, and when one person is acting alone, the team is impaired significantly. The ability to deliver the killing blow requires everyone to be working towards the same objective, and to see the same soft spots. Knowing who your target is as opposed to who your friend has allocated as his, and instigating the attack and hitting your target at the same time (as opposed to starting at the same) will make or break that chance of a successful take-down.
Keep each other informed of events, are you taken, are you freed, are you behind, are you in front, are you struggling, are you exploring – (having a microphone) and being able to tell your team mates what you are doing exactly when you are doing it will assist them in their desires to stay in sync with each other.
Keep one eye on the clock, one eye on your friends, and one eye on your vulnerabilities, and you will be fine! Of course, it's impossible to keep an eye on more than one thing at a time, let alone be able to use each eye independently so that's why you must try to use every sense the game has given you in order to multi-task, so use your ears as well as your eyes and speak!
The only thing you then have to rely on is your skill, the skill of each member of the team and the skill with which your team can collaborate to formulate the attack or escape. Knowing not just how to attack but when. Whilst I agree with myself that each team requires someone to call the shots, each player must be equally capable of recognising and doing the same, even if they do not have the tenacity to do it themselves. As the game can roll in so many ways, differing in combinations, changing the flow of the situation so drastically, it thus boils down to how well you can reach the best decisions quickly among yourselves.
I hope this helps you understand areas which may not have already been accrued from experience, and will give you an insight into some things which you may have known or not. This serves as an introduction into the psychology I feel a competent team requires to succeed in Left 4 Dead 2.