If playing on my own in a folk club, I might limit myself to simple polkas. It depends on how nervous I'm feeling.

In sessions, it can be more a matter of who I'm playing with although I'm always a slow starter and it takes me a while to relax. Obviously in some sessions, you can start just about anything and others will take up the tune strongly but there can be other occasions where let's say I'd rather keep to tunes like the Kesh Jig which I know I can usually "keep control of" (esp on tenor banjo) rather than perhaps have the tune taken in all sort of directions or perhaps come to a grinding halt if I miss a note or two.

If I'm playing with one other, I usually prefer a good guitar player. One who can find the right chords (some off chords really distract me) and who will really go for the tune (and I don't mean just thrash the guitar) and keep going (I have a hard time with the player who will try to wait and or adjust if I slip up. Instead of being able to correct my mistake, I find 'm then adjusting to get to where he has tried to correct on my behalf...).   I find sort of player a good sort of "safety net" if I'm trying something a bit harder or don't play often.