As I’ve talked about previously, if you’re having random lag or high latency try running through a proxy.There’s more information about that here. I’m down to 70ms now in arenas – compared to 250ms it’s ~very~ noticable (a good test is to use Fan of Knives and check the delay between the keypress and the animation/sound happening).

Once you’ve got your connection running as smooth as possible, it’s worth trying out a very useful addon called SnowfallKeyPress. By default, when you press a key you have a spell bound to, nothing happens until you release your finger off the key. This addon changes that, so as soon as you press a key the action takes place. We’re not talking about massive time savings here, but hey, every little helps!