Warm up your vocal chords before you sing. Try humming or singing scales. This will increase the range of your voice and help protect your vocal chords from strain. Warm up for at least 10 minutes before you start to sing.
Relax your body using relaxation techniques at least 15 minutes every day. Being tense can limit your range. Close your eyes with your arms hanging freely at your sides. Concentrate on taking slow, deep breaths. Allow your head to fall slightly forward until your chin rests on your chest.
Run on a treadmill, take a brisk walk, go swimming or play tennis. These types of aerobic activities will make your diaphragm strong and will allow you to develop a more powerful voice, which will hep with projection and endurance.
Practice singing as often as you can. Treat it like a full-time job. The more you practice, the better you will be. Be careful, however, to avoid overuse of your voice, which can make it hoarse and strained. Practice for as long as you can without feeling vocal discomfort.