i usually aim them fairly low, so i can see under the fog, as they should be used.
if theyre nice and low, projecting along the ground, you can center the beams nicely, to get good coverage.
if you want to use them as driving lights, which most people seem to want to do, then i suggest Deans foglight bulb mod (at least i think i saw it on his page) and the foglight wiring mod.
then, aim them up a bit, so they project further (50 yards??) and you need to aim them so they wont blind oncoming drivers, basically meaning just that the drivers side gets aimed inwards a bit more