I didn't see any of this on MMOwned when I searched.
Get out of reach of Pets
There is a spot in Blade's Edge arena on the south side where you can drink and pets cannot reach you. Here's a SS of the spot: ImageShack - Hosting :: bespotll7.jpg
Very rarely, the pet might jump and hit you. And occasionally if the pet was sent to attack you from above, he can hit you from the ramp. More often than not, however, this exploit works.
Best thing to do is to kite the pet down to the bottom then hop behind. This is known to work against scorpids and felhunters. Not sure about bigger pets like felguards.
Heal/Nuke someone in combat and drink afterwards
We all know it takes 5 seconds of non-pvp action to drop combat in the Arena. Whether you are a healing or a dps class, you can take advantage of server lag to get off a heal/nuke and drink right afterwards.
All you have to do is sit tight for around 3 seconds. Now start casting a big heal, or anything that wont finish casting before the 5 seconds is complete (shadowbolt, frostbolt, anything DD). As your spell is about to finish casting, spam your drink button. You will cast the spell, drink, and then be in combat but still drinking. This is an insanely powerful trick if you are a healer or caster.
Blade's Edge Kiting Tip
On the ground floor in Blade's Edge there are wooden supports for the bridge right next to the ramps. You know, the poles that you use to LOS people who are on top of the bridge. There is a little space between the ramp and the wooden pole on the ground floor.
If you are a troll, Blood Elf, Gnome, Night Elf, or Undead, you can almost always run or jump through this space, especially on the southern side of the arena. However, Taurens and Orcs cannot fit through here. This can be very helpful against tauren and orc warriors (which it seems like all warriors are). So if you are trying to kite that warrior and want to build a little space, run through there if you find yourself on the ground floor. Again, this trick works better on the southern side of the arena than on its northern counterpart.
Hope these things help you out in arenas :-)
Edit: Updated Link to SS