Introduction to PvP
Player versus Player combat.
This guide assumes you have few PvP experiences, especially in Guild Wars. You might be trying the arena in Ascalon, or you might be in Lion's Arch or the Tombs of Primeval Kings if you waited to be high level before you try out this aspect of the world. You could also begin your PvP in guild versus guild, which gives you the advantage of knowing your teammates better (hopefully) but the same is true for the other team. Your experience will vary a lot between these arenas but there is something human you must overcome wherever you might be: yourself.
Be aware of your surroundings. Most people have tunnel vision in PvP; they are only focusing on what they are doing. Things such as watching the health bar for healers, watching the guy you are attacking for damage dealers. Good practice for being more aware of the entire battle rather than one guy is to make a character that interrupts or weakens enemies. For example certain ranger, mesmer or necromancer 'builds' focus on interrupting spells, or slowing down the movement of enemies. You will most likely want to apply these effects on more than one opponent since the effect lasts long enough for you to permit yourself to do so. Looking for more targets forces you to look around, which gives you a better global perspective. If you strengthen your party with 'buffs', then you get better at the third point.
Fear/rush. You might not realize it or think you are too much of a pro to feel it, but the fear that comes from uncertainty is your first obstacle. Much like the first time your toes touch water before you start to swim, the first time you go to a new school, or the first time you begin a new job, you feel like you have no idea what you are doing. This is fine; to win an Olympic medal at swimming, you have to have entered the water for the first time at some point. The best thing to help you with this is dying. This allows you to calm down.
Know how far you are from your healer. Before you get better at 1), you will probably have a hard time doing this. If you want to stay close to healers without too much effort, play a caster or ranger that doesn't melee.
Know what is going on. The basics of this are simple. Simply press 'T' when someone announces that they are attacking someone and join in. However it is also a good idea to know what skills your teammates are using so you know how to compliment them. This requires coordination and knowing in advance what the other people in your team are bringing. Might seem like a hassle, especially in the arena when you don't have time to discuss anything for long, but it pays off. Likewise, know what your enemy is doing. At this time, this is pretty easy. If you see someone who is a W/Mo, you know they will melee. If you see an E/x (any other class) you know they will either lob fire spells at you or water tridents. If you see a Mo/x, they are the healers. The other classes are trickier, but you can assume they are support. This will likely be less obvious as the game (and its players) matures. In any case, once you know who does what, which might require half heartedly attacking while looking at what the other team is doing, you can decide who dies first. In most groups at the time of writing, this is usually the healer(s) or primary monks. Either way, it is important to know who is doing what so you know who is more of a threat to your plan.
Know what the health bar graphics represent. Yellowish/brown is poison or diseases, pink are dot (damage over time) hexes, pinkish red are conditions (bleed etc), arrows pointing down are the other hexes, arrows pointing up are positive enchantments. Especially useful to know for healers, but also good to know for other classes so you know what is going on and if you can do something with it such as spread it with epidemic, drain it for health or mana or block it.
Know how to listen/follow. If someone else is taking the role of leadership, you should do what he says even if you don't agree with it. You can give your input and suggest something different but ultimately, only one person should be the leader and make the final call. If more than one person is leading, it's as bad as no one leading. You also want concise and clear commands. The same goes for target calling. It is best if only one person calls targets unless there is a prior agreement that certain people follow one caller, and other people follow the second caller.
These are some guidelines to help you playing PvP. Once you get used to the arenas, you will find yourself less nervous and more calculating. You will learn which 'build' works best for you and you will excel if you put the effort into it.
*** This article was written by delicious_doctor and because it is great guide for people who doesn't play PvP yet, I posted it here. :)