Some really good advice here for sure.Here best I can tell you from personal experience.
Be totally and completely prepared.Do this by not being late in setting up your stuff.Get to the place before anyone starts to perform and is almost empty of folks.If it is a place that already has the set up try to get the person in charge to let you try it out.If you are the one setting up your own stuff do so very early on.Some stages are notoriously bad accoustically and if you have not heard yourself beforehand it can startle you.
Once you are satisfied that you know and understand the setup and are comfortable with it then try to get to know some of the folk that run the place so you feel like you are more at home.If possible,go the the place sometime before you are to be on stage and before the crowd builds.This will again make you feel more at home.
Remember you are in fact communicating with every person in the place whether it be with music,dance,comedy or whatever.Sell your message with exuberance and they will love you.
I hope this helps.I still get nervous every time I get up in front of people.I could not even do it at all until the age of 33.Once I overcame the fear I experienced the greatest high I have ever had bar none.