Depends on the pants. The rule of thumb I use is the front clip on my holster goes right behind the little pocket watch pocket, so I can shove my cell into it and not have the metal clips scuff it up. That usually puts it at about 4:00-4:30.
I don't have a SET position for my holster. I always have both of the clips on my MTAC between the 1st and 2nd belt loops on my pants. I guess that varies slightly with the brand of jeans, but usually always works out to about 2:30. I find that the belt loops help to keep my holster in position a little better.