Knowing theory would probably be the ultimate and obvious answer; since its essentially the language of music, so if you know how to speak it the better you will do with others.

Yet that is the problem, no matter how much you may know theory, if the people your playing with dont know theory than it probably wont help ya much in terms of communicating.

So which comes to this point: Everyones skill level/music knowledge is going to be different, sometimes vastly different. Same with their music influences. You pretty much have to just jam with as many people/bands as possible until you find the certain somebody or the certain group of people that you "click" with the best, wherever there is that chemistry.

A good example actually is concerning one of my favorite bands. The band consist of 4 members. The singer/guitarist literally writes all the music. Recently the band lost their drummer and the second guitarist. Oddly enough their sound is now quite different; even though its still the same single guy writing all the music. I think that is good example of what a different chemistry/vibe can do.