Join Date: Apr 2008
Location: St. Pete, Florida
There are two main aspects of handlebar position: height and reach. There's no "rule" for reach, but if it's wrong, you'll probably know it. If you feel stretched out or crunched up, reach needs to be adjusted by getting a longer/shorter stem. Some fitters suggest your upper arm will be at a 90 degree angle to your torso if you have the proper reach, but letting comfort be your guide on reach is just as effective.
Height comes down to how "functional" you are. You generally want the bars at the minimum height at which you can remain comfortable on your longest ride. The amount of flexibility you have to tilt your pelvis forward will determine how low you can have your bars. The goal is to have a relatively straight spine when riding. Core strengthening (particularly abs) may help correct muscle imbalances that contribute to poor pelvic flexibility, but that's not the only possible cause. If you have to significantly arch your back to ride, then your bars are too low.
Photograph yourself on the bike can be helpful for checking your bar fit. If you have a stationary trainer this is relatively easy. If not, you can try to prop yourself up next to a wall (but note that holding yourself in this position may cause things to be a little different than when you're actually riding). With your hands on the bars and arms slightly bent, you should have a relatively straight back. But in the long run, the only way to find the "best" position is trial and error.
Also note that bar height affects reach. As you move the bars up/down, the reach will shorten/lengthen due to the angle of the head tube. As such, it's best to get height worked out first, then fine tune reach.