I'm not a great soloist, so in a jazz situation where a solo is expected (not already written), I usually like to do an embellishment on the melody. I'm currently playing in a small group - bass, vocal, guitar - so any sort of far reaching exploration would likely be lost on the audience as well as the other 2 band members, especially since the vocalist will have stopped singing. The guitar player can comp decently, but it's usually best to just have one pass through the melody with me taking the lead - based both on my desire to return to my part and the inevitable breakdown that tends to happen without me keeping time. FWIW, the guitarist I play with is a UNT jazz guitar graduate, so he's definitely better positioned to do the soloing, which he often does. I may only "solo" once or twice per night. It usually only works for songs where hearing the bass take the melody adds an interesting twist to the song. If I were playing in a larger group, I would probably only want the drums to keep the beat and then either a piano or a guitar to comp for me. Most accomplished players could also benefit from having horns or other players come in at an opportune time now and then. The main thing I would agree with from other posts is that it's bad form for other musicians to be noodling around over someone else's solo. It's one thing if you want to comp and support what is being played, but it's another to just randomly play over someone else.