Warm up your vocals before you try to project them. Projecting without warming up first can damage your vocal muscles and vocal chords. Yawning and running through vocal scales are examples of vocal warm-ups.
Practice breathing in and out. Breathe deeply from your gut and not from your chest. When you breathe, place your hands on your stomach and make sure that it is moving in and out as opposed to your chest moving in and out.
Relax your throat and your mouth before you project. Do not clench your jaw or tighten your throat as this will tighten your vocal chords and prevent you from projecting as loudly as you can.
Spread your legs and arms so that air can pass easily through your body and push your voice from your diaphragm up and out through your chest, throat and mouth. Practice this, remembering to enjoy your performance and to relax as you project, as this will help your voice to project even more.