This is how I did strictly from the point of view of ergonomics. Sit down like you would when riding. Hold your arms in the position that you would when riding and grasp the handlebars. The rise should be naturally in line with your wrists and brake levers so as to not bend your wrists / arms / back / shoulders at a wierd angle.
Essentially that will place the bar towards you (I don't know degrees because every bar is different mine is slightly less than 0). Make adjustments where you think you need it. BMXers tend to like it more tilted up. I find that very uncomfortable for riding trails.
Cheers.