PVPing on the shaman I would recommend getting a core set of totems to drop initially.
(if you can reliably get all your shaman in the same group then you can drop a load of different totems that will help all of them).

More often than not i'm finding I'm not in the same group, so I drop a lot of the same totems on each one.

Rotation wise you are mainly going to be throwing lightning bolts. Using chain lightning to hit a warlock/hunter pet and jump to the warlock/hunter, or when there are loads of enemy all together. Flame shock, lavaburst for some guaranteed single target nukage (have a button to trigger elemental mastery for instant cast lavaburst).

You'll tend to be a lot less mobile when multiboxing.... although I'm working on being able to move as a group more.
Very important when being AOE'd. I'm putting talents so earthbind stops snare effects so I can ghost wolf and get my team out of the massive aoe that focuses on you when you have a group that know what they are doing.

I'm still learning though, but it is great fun.

Oh one final tip - get a spread out macro - Great against melee that like to weave in and out of your guys or bladestorm you down.