I don't really believe there are any steadfast rules in music–only guidelines for us to follow, and, occasionally, stray away from. While it's important to understand that set of guidelines before you necessarily break free of them, the end result can be oh so sweet.
The combination of major and minor pentatonic scales is something every guitar player should understand.
If you're looking for that "outside" sound in your blues soloing, you need the altered scale in your life.
Learn the surprisingly useful fingerpicking technique that John Mayer leans on for some of his songs.
Imagine you could get in a time machine and round up a handful of the best living and dead blues guitar players ever... who would you choose?
These chords will make you feel luxurious.