I spend as much time as any guitar player tweaking knobs to find great tones. Here are some links that have helped me in the quest:
First, the effect of pickups on guitar tone:
Even though we each have different ideas about our ultimate tone, I think we’re all looking for a rich sound – rich in harmonics, that is. Lots of harmonic content = lots of ‘tone’. If you have lots of harmonic content to start with, you can easily use other sound shaping tools (tone controls on the amp, in particular) to sculpt your favourite and unique sound. It’s a bit like giving an artist every colour he could wish for to paint a picture. If you only give him a pencil, he can still draw a great picture if he’s really good, but has limited options.
The best rock tone is from saturated power tubes directly driving a guitar speaker hard, with no load or attenuator getting in the way. The only really satisfactory way to get actual cranked tube amp and speaker tone with almost no room noise is to use a speaker isolation cabinet and its attendant gear.
Finally, the mother of all pages: Derek Miller’s collection of articles about guitar tone in rock’n’roll:
Perhaps the stereotype rock tone is that of the Marshall stack: a rectangular, 100-watt (or more), tube-powered amplifier “head” stacked on top of two speaker cabinets, each containing four 12-inch speakers. In this case, the guitar is a bit less important to the overall sound, although most who prefer it use Gibson-style solidbody guitars like the Les Paul or Gibson SG, with dual-coil “humbucking” pickups. Cranking up the Marshall creates a buzzing, distorted, complex, and extremely loud sound.