Chances are if you're reading this, you're interested in music theory. I want to preface this lesson by encouraging you to check out Guitar Super System if you're not familiar with intervals on the guitar neck, as it will be infinitely helpful to have as foundational knowledge. The Altered Scale, AKA the Altered Dominant Scale, AKA the Jazz Scale, AKA the Super Locrian Scale (had enough yet?) can give you that "outside" sound you might be craving if you've been playing the same old blues licks and are in search of something more. The best use of the scale is implementing as chords change from one to the next, because hanging on this altered sound for too long might make you sound like you're hitting a bunch of wrong notes in a row... beware the power. ;)
Prepare to play the most meaningful music you ever have.