Thanks to Paul Glaves, Technical Editor of the BMW Owners News
Getting a correctly aimed headlight is straightforward. You need to make a couple of measurements and then aim the light at a flat wall, as follows:
With the bike upright on its wheels (off the side or center stand) and your weight in the seat, have a helper measure the distance from the floor to the center of the headlight lens.
Pick a flat wall where you can locate the bike on level ground so the headlight is 17 feet from the wall. Place a horizontal mark on the wall two (2) inches lower than the height of the center of the headlight.
With you again sitting in the seat adjust the vertical screw (usually at the very top or very bottom of a headlight next to the lens but inside a trim ring) so the flat top of the low beam is just to the line you put on the wall (a two inch drop at 17 feet).
The horizontal adjustment (screw will be on the left or right side of the headlight lens) should center the beam ahead of the line of the bike.
If you have spotlights use this same procedure to aim them.