The trick is learning that what sounds good by itself can be terrible in the mix. In a live context guitars often have to be eq'd more towards the treble end as bass and drums (and often keyboards) take up so much real estate at the bass end of the spectrum. Pete Thorn recommends that guitars always have a low pass filter taking out any sub frequencies. In a recording context compression and stereo spread also do a lot to make guitar stand out more.
I always have my amp set pretty bright as eq is better than volume if you want to be heard.