What is your character's career?
What role will your character play in the adventure? How did your character get into this line of work? What asperations does your character have in his or her field?
Choose your character's career (which remains with him permanently) and your starting specialization (which may be only one of many your character undertakes over the course of his story) from any of the lines. Each Career gives you career skills.
It is a good idea to look over all of the options before deciding. The idea is not only to look at the immediate capabilities of a character, but to look forward to that character's growth potential. If you imagines your PC will one day fly a small freighter into certain doom in a desperate battle for the galaxy, it's a very good idea to make sure good piloting options are along the chosen development path.