Re: Pickups
What Dave74 said is pretty right on. The only extra thing to consider is if you use your neck pickup of middle pickup (on a stratocaster/les paul custom/stuff with a middle pickup) more. Then you would blend the others around whichever one you use more often. The general rule of a distance of 4/64" high E and 6/64" low E, usually measured from the screw poles, and while freting the last fret is a good place to start though. I was using a Screamin Demon in the bridge with a Phat Cat in the neck (to experiment) and I ended up having to drop the Phat Cat to like 9.5/64" and 11.5/64" to try to get them to blend better, otherwise the Phat Cat was huge in comparison. But Usually when using a JB and 59, or Custom and 59 I end up at pretty much that whole 4/64" and 6/64" no matter if I measure or do it by ear (which takes so damn long). I like measurements because I can spend less time listening to the minute changes in tone, and more time listening to melody. Either way, don't be afraid to mess up your pickup heights. You could find out that you like the pickups farther away, or much closer. Not much to lose by screwing around.