I started off by leveling my rogue in BT, but the crowds were far too large. Oddly enough, though Horde has always been the primary faction on my server, we were way overcrowding them. Is BT the Alliance area, while HF is the Horde area? How do I get to HF from the Alliance side?
Anyways, since it was so crowded, I decided to make my Death Knight. I was going to go Dranei Female (made a sweet looking one), until I realized the cape sticking overtop of the tail just doesn't look right on a plate user. So, I decided to make a Human Female. Kind of a bonus, since Humans have the most OP racials in the game, IMO. I used to hate the Human (both female and male) faces, but one of the 3 new Death Knight exclusive faces I like.
I was going to go Frost, since it seemed like fun and a great group spec, but I decided against it realizing I wouldn't be doing too many instances in Outlands. Went Blood for the low-downtime factor.
Oh, and if you're a DK, a Rune mod is a must. I got RuneMover, which let me move and resize my rune bar. It's right below my character now. I just wish I could make it slightly transluscent as well. Along with ArcHUD, I don't need to look at the top left of the screen ever again.