Firstly you measure the distance from PU to string when you fret at the highest possible fret. That is the standard and more telling due to guitars being set up differently.
Secondly, really just try different things and listen. The sound will change not just in terms of agression and you will need to pick up what you like.
Have it set far away and go by increments of 1 screw turn at a time up and spend a few minutes there. Take note of the changes (and the positions. At least mark how many turns in you are, best if you also add measurements). Do this until you get unwanted overtones and things just sound cr@p.
Then you got an idea of how the height effects the tone and you can go back to the area you most liked or revisit some more.
Then of course finetuning.
Lastly you can (do not have to) raise the pole pieces. This adds some clarity, definition and treble cut in general. Not really that important for the AM, but for things like the Crawler this really works wonders imho. Sometimes people like to raise the wound strings a bit and leave the plain ones alone.
I raise mine about 1mm or so.
