Handlebar position

Put your handlebar in a position you feel comfortable riding with... If you don't know, try different positions and go with the one feeling best... It's not harder than that.

There is no right or wrong. 

Most companies have a reference mark on the bar mount, used with these lines on the handlebar it makes it easy to return to your preference. 

You can make a mark on your mount as a point of reference. (paint or small engraver)
 

In lines with forks, so look from the side and just use the marks later if they move or you remove them.

Assuming same mounting holes are used, the more you roll them back the less pressure on front end. More fwd than in line, more nervous it will be and at least for me easier armpump.

I would advocate for in line with forks. Change bars if not happy with that height or sweep.

Shorter people can roll back with less negative consequences.

I usually run mine so that the line created by the crossbar and the main bar is parallel with the forks. (If you do not have a crossbar, use an imaginary one as your guide.) 

A slightly forward rotation will allow for easier elbows-up form. 

EDIT: PS- The markings can be used to make sure your bars are adjusted equally left/right as well as marking the rotation. 

0 should be neutral. I have a Protaper and an Odi bar that the markings seem to be a little off on so don’t 100% trust them.