Watch the Rhythm Drives the Solo online guitar lesson by Henry Johnson from Jazz Expressions
When I'm playing, I'm always listening to everyone around me, and I take my substitutions from the bass player. The bassist isn't going to just play four notes on one chord - they could, but it wouldn't move around as well - he's going to walk up and down. What I do is take some of the note's they're using and use it to reharmonize everything. I don't have to play every chord that he's playing, but I have the option to use his notes as my color notes. This will help me drive the rhythm and create new melodic content.