If you are undecided about which crafting profession or which crew skills to take on (especially if you are rolling an alt.) choose slicing. Yes, slicing got nerfed not long after launch, but you can still make money from the profession. The lockboxes are still yielding credits, just not as many credits as they once were. Also, the crafting missions that you get along with the augments still sell well on the GTN, so you can still make a tidy profit slicing.
In addition to slicing, pick up a couple of gathering professions as well. That way you can pick up resources while you are running around until you finally decide which crafting skills you want to fully develop. Raw materials/resources always sell and you will have plenty of them if your crafting profession won’t have a use for them.