Matt Warnock has posted a nice article outlining theories of practicing jazz guitar, but his thoughts apply to any type of playing. He offers advice on developing improvisation skills, how to bolster muscle memory and the idea of practicing when your instrument isn’t even in hand:
Here are some of my favorite ways to practice away from my guitar:
Running through chord changes to tunes I’m learning in my head
Saying the notes of modes, scales, arpeggios and chord voicings in my head in all 12 keys
Soloing along to a tune and just visualizing my fingers on the fretboard, imagining how it would sound on my guitar
Read the entire article at Matt Warnock Guitar.