Some quick tips, for recording on a Saturday night:
Monitor through different sources while mixing and mastering: As you work, periodically check your mixes through near-field monitors, HiFi speakers, computer speakers, headphones, even an old boom box if you have one. As the mix nears completion, you’ll be much more confident that your work sounds great in any listening environment.
When recording electric guitar, add a 2nd mic near the guitarist’s ears: Guitar players naturally move to a spot where their amp sounds best. So along with a mic directly on the amp, use the guitarist’s instincts to your advantage, and record the sound that the player hears.
Get the sound you want before pointing a microphone at it: It’s easier to capture the right sound when it sounds right.