Paladins are among the top in PVP and therfore are invaluable if played right. However they are hard to get right and easy to get overconfident. Ironically the level 80s are more likely to make the overconfidence mistake compared to new players. This guide should help you to master Warsong Gulch.
Before the battle, waiting in the hold, many players will likely ask you for buffs. If a better class for this is there and available, don't buff but ask them to. If you should do it then be careful about mana, you will need it. You should do a final, overall check and attack. Make sure you fall out with the rest of the party and go fulfill your role.
You should be buffing and healing while guarding others. You are usually a guardian type, helping the others complete their goals and healing. Keep your mana with you and don't waste it on Retribution or Protection talents. Generally you should stay with the flag carrier and keep them healed and buffed.
You should either flag carry or divert. Carrying the flag mean, while guarded, you will have the opportunity to take damage anyway. Causing mayhem and disruption among the enemy side is something that you can do.
Your primary role is that of an arms or fury warrior, dps. Usually your job is to fight, fight and fight some more. You can usually work as that of a guard or distration. Just try and avoid damage as, while you can survive it, that is not your role and you would likely confuse the actual tanks.
This job involves charging into the enemy hold, causing chaos and not leaving until you're dead. Dynamite and any kind of explosive is very useful here. This cannot be stressed enough. Also, tanking is a highly reccomended role for this job if using dynamite. If not then stick to dps.
This job is not suited to a paladin as they are slow and ponderous, not stealthy and have many reasons to be attacked. This role is more for rogues or night elves and anything stealthy and agile. However due to these facts, many enemy players can disregard you in that aspect and mistake you for something else.
If your crew is veteran pvp then they will probably have seen many paladins before. You might have to work hard to impress them but they might disregard you. This is highly unlikely. Do not leave in the middle of an instance as Paladins are overplayed sometimes and your crew might disrespect the next paladin to come along. See Loladin.
See Paladin PvP guide for further info.
Druids and Hunters can be hard to spot here. You may only notice their attacks after it's too late.