Acquire complete comfort with your performance material. When you are singing, you should focus on the execution rather than frantically attempt to remember lyrics, notes and entrances. Natural nervousness can amplify into full-blown stage fright when you are not secure with the material.
Thoroughly warm up your vocal chords and body before a performance. The first affects of stage fright can strongly increase tension in the throat and various muscles throughout the body. Preempt this problem by doing vocal warm-ups, moderate limb stretches and deep breathing exercises.
Immerse yourself in the appropriate emotions of the piece and allow your performance to follow suit. Vocal performance is not only entertaining but cathartic for both the singer and the audience. Staying in the moment, as opposed to anticipating mistakes or mishaps that haven't even happened, will push your stage fright to the back your mind.
Connect with your audience. One of the scariest things about performing is the idea that everyone's eyes are on you and you alone. You can overcome this fear by feeding on the attention of the audience rather than dreading it. Make eye contact with individual members as if you were the only two in the room, essentially drawing them into your performance.
Genuinely enjoy yourself. This might sound simple, but it's easy to allow the anxiety of singing in front of an audience to eclipse the reasons you wanted to sing in the first place. Replace the pressure of not making a mistake with the intention of having a great time.