1.Tune your instrument before the session starts - at the very least take the bloody thing out of it's case.
2.Decide what songs your going to sing before the evening starts - that way you don't have to flick through sheets - if you need them.
3.Don't try to sing songs you don't really know - if you don't know them, keep them at home until you rehearse them enough to know them. 4.It's bad manners to inflict your half-arsed, unrehearsed efforts on other people.
5.Keep your intro's short-you may love the sound of your own voice, others rarely do.
6. Learn the words - no excuses for not apart from laziness. Case in point; my brother has gone onstage for forty odd years with a sheaf of lyrics. He's been having eye problems lately, cataract, etc, and suddenly he's managing without the lyrics because he HAS to - he can't see the sheets.