For starters, learn to use your instants. There's nothing worse than cast times in pvp. A priest shield can eat an eviscerate or a frost bolt crit. You can cast that thing every 15 seconds on the same target, and until you run out of mana on multiple targets.

Drop a renew on that rogue. They are the masters of managing their health. All renew does is make it easier for them. Same goes for warriors. Fortitude is great, but it destroys your mana. A well-timed shield is a lot better.

If you're shadow, open with vampiric embrace and ONLY use mind flay. Snares are incredibly powerful in Warsong Gulch because of the dynamics of flag chasing. This becomes doubly powerful when you consider the very low mana costs of vampiric embrace and mind flay.

Once you've learned your instants, then you can start using spells with cast times. That's the subject of the next article.