I just pound down glutamine and "feel it out"...After years of training, you can really just gauge when it is time to hit the muscle again....Soreness, weakness, and a lack of energy in the muscle are ways that one commonly uses to determine muscle recuperation...
Stretching is a method alot of bodybuilders are using to recuperate quickly, by this I mean 30mins + stretching, not 5 minutes at the gym...this is a concept I am trying to find time to incorporate myself.