I'm not a singer by any means, so I'm going to give some tips from an acting stand point and I hope they help. If you are a singer then maybe you can tweak these pointers to be applicable to a more musical stage presence.
There is no guaranteed way to completely get rid of stage fright, but here are three ways to lessen it.
#1 Practice makes permanent. It is a common misconception that practice makes perfect, but the truth is that only perfect practice makes perfect. When you practice pretend you are already performing. Every word, inflection, gesture and expression should be intentional. If you practice poorly, you will perform poorly. However, if you practice correctly you will be stepping on stage with the confidence that the likelihood of you messing up will be very much reduced.
#2 Step into your character. If you have developed your character well, then you should be able to become him or her from your first step on the stage. You can even create a back story for your character if it helps you. Practice gestures and expressions in the mirror and even improvise lines to your reflection. Doing this will help you cover yourself if you do miss a line or a motion on stage.
#3 Don't tell on yourself. When you're on stage, just remember that the majority of the audience doesn't know what you're supposed to be doing. If you mess up, just roll with it. Improvise to fill the gaps and move on to the next scripted line or motion that you remember. The audience will never know the difference, so don't sweat the small the stuff.
I hope these tips help. 3nodding