Bingo! Also don't be afraid to drive stylistic direction. You will be amazed at how significantly you can change the overall feel of a jam by your choice of groove. You can get 'tight and technical' and turn the thing into a Yes/Rush-ish thing or get really laid-back and loose and bring out the Marley of it all - all within the same jam. Also - if the opportunity presents itself and you want to solo, don't be afraid to take a little time and let your solo unfold. I don't know about you, but I am no Victor Wooten. At first I used to shy away from even trying just because I couldn't "shred". Since then I've learned that being melodic, lyrical and creating phrases that are logical and relate to whatever melody and style have been established goes a LONG way to creating a really nice solo. So it doesn't have to be "shredding" to be impressive. It can be very simple and still be really great. Oh yeah - (ironically, since I am now rambling!) but LESS IS MORE!!! Don't be afraid to even pull out entirely every so often if you feel like the groove has stagnated. Sometimes holding a single whole note after you've been grooving on a syncopated line for a lot of bars can open up the feel and prompt the rest of the group to alter their tact too. This usually brings on a really welcome change and new ideas bloom in it's wake. But as Mojo-Man said, lock with the drummer and provide a rock-solid foundation for everyone to jam over. You will be loved and respected forever!