Took my CB500 for MOT last week and asked what it would cost to have the headlights on my Wee corrected as I had to lower them myself cos I was getting flashed (blinded) by oncoming traffic. This is what he told me:
Get someone to sit on the bike on a level surface and measure distance from ground to centre of headlight bulbs.
Put a line at that height on a suitable board or wall.
Move the bike So that the headlight is three feet from the board /wall and select main beam.
The light should be on, or just below the marked line. If its higher or lower, then make the necessary adjustment.
Haven't tried it yet, so not sure if it will give a satisfactory setting, but I think I would prefer to have it set using the proper equipment, just for peace of mind.