Which Proffesion

It really depends on what you want to do with your character and what class you are. If you are looking to use professions as a way to make money then I would suggest that you pick from Mining, Herbalism, Enchanting, or Skinning. Which ones you pick depends on what you like doing and which supplies sell for the most on your server. On some servers Mining is the most profitable but on others it may be Herbalism or Enchanting. Keep in mind that when you do these professions for gold you are selling the materials.

If you want professions that will benefit your character gear wise, which professions you choose really depends on what class you are. It's hard to tell someone which professions to pick if you don't know what class they are and what they want to do in end game content (PvE or PvP or both).