I always just think of characters I like, or traits I find desirable or interesting in people and just make a character based around those. To be fair, I usually have a pretty good idea of what kind of character I want to play as soon as I join a game based on the setting it's in and what's going to be happening. 
Scott was pretty easy because I knew I'd be taking a fairly proactive role and that he had to be functional as a person enough to actually manage to get to the point in life where he could be a pilot, so I just put together the right traits and things I found positive enough, and added in a dash of aggro enough to make him interesting.