make contact with the audience as soon as you can . if you can make the audience laugh you are one step to getting them on your side, say hello., or good evening
if you feel nervous take a deep breath this sends oxygen to the brain relaxes you and helps you perform better, before you start singing yawn, but not in front of the audience.
plan your first half, it should have a beginning a middle and an end. but be flexible for example, if the audience are joining in choruses include more chorus songs, make sure you vary your tempos and your keys, to avoid sameiness.
listen to the other singers this gives you a clue to the feel of the club.