The best advice is to relax, stay away from the booze, look professional and play the kind of music that they want to hear. Unfortunately, most of the time they will not tell you, but most likely they will range in age from 50 to 75. Therefore, most of the music they grew up on will be from an era that was when they were 15 to 25 years of age, or stuff that's from the late 50s to early 70s. This doesn't sound like a crowd that would enjoy hard rock, but you can be assured they'll dig on Sinatra, Ritous Brothers, most Cole Porter arrangements, and some doo-wap stuff.
As for the jitters, everyone gets them, especially early on, but if you relax, and try to have a good time yourself, this is often contageous to the audience.
Good Luck,
Gary
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