Headlight aiming

I noticed my driver side headlight is aimed higher than the passenger side. I have not been flashed yet so I am thinking the passenger side is to low. I can see when I park in front of a wall (about 18 feet away) that the driver beam is higher. Is there an easy formula to adjust? Are there marks to line up the adjustment screws on the housings? These are factory lights on an 03 GMC sierra 4x4 ext. cab Quadsteer.
Thanks

You need a large wall for this. I used a cement wall behind a strip mall. Park the truck so that the front bumper is within a few inches of the wall, and make an X with duct tape where the lowbeams shine brightest on the wall. Then back up 25 feet. The brightest part of your headlights should be shining about an inch lower than the duct tape.