I also raised the height of my headlights. It was very hard to see clearly in the dark on unlit or poorly lit roads. Cannot remember how many revolutions I turned the white adjuster, but using a brick wall in front of the car is a good idea. Plant the car on a flat surface before doing this. If you remember the starting point of the adjuster and note the amount of turning (like srhutch says, in Degs, then it's easy to do the same to the second lamp on the other side of the car.
In terms of 'knowing' an appropriate angle to have the lights, be sensible when adjusting and use the road and other road users as guide, and if no-one flashes, then you're probably okay.