The clefthoof is nice because he has extra armor, gets a bonus on healing received, and has a defensive cooldown similar to my turtle shell, but he can occasionally get in the way because the model is just so darned big. Personally, I mainly use a spirit beast or a clefthoof: spirit beast by default for the heals clefthoof if I'm in a dangerous place and need a tank, or if I'm in a dungeon group that doesn't otherwise have Hero or Time Warp. Once you know what families you want, browse to see what pets are available in each family and where to go to tame them. Once you hit max level, if you're looking for the best pets for doing particular kinds of content, I'd start with the hunter pet guide on wowhead. I don't do PvP myself, but cunning pets are recommended for that. For now, I'd suggest having at least one ferocity pet, and at least one tenacity pet. In my experience, pet abilities are really important mostly at max level.
