with all due respect, just pick some professions and level them. and play what you think is fun. blacksmithing is pretty safe that it's good for just about any spec.
idk if you're even asking this but for raiding there can be some professions that are better than others but it kind've depends on what class/spec you are, and since you didn't pick 1 yet, it's pretty hard for anyone to give you advice.
Once you find something you like, go research the crap out of it
Engineering is definitely something you want if you can get it. The boosts coupled with on use gloves are great, plus you get a glider :P
Another profession is more dependent on what you are playing. Like the poster above me said, Blacksmithing is always good, but some classes can benefit well from Lifeblood herbalist or the passive from Skinning while other classes don't need that stuff. Crafting your own gear is also hugely helpful, I know that for cloth wearers you cant go wrong with Tailoring because of the embroidery.