Practice good vocal health techniques to keep your vocal cords in working order. Stay hydrated with water or herbal tea, avoiding caffeine and alcohol. Do not smoke or spend time in places where you are exposed to second hand smoke. Get plenty of rest. Eat a nutritious and balanced diet. Avoid straining your voice by yelling, cheering or talking in loud places. Wash your hands often to avoid catching illnesses. If you have a cold or a sore throat, avoid using your voice. Whispering is more injurious than talking quietly.
Relax the muscles in your entire body before beginning to sing. Tension anywhere in your body can translate into tension in your vocal cords, which can cause injury to your voice. Any relaxation technique that works for you will suffice.
Stand up straight. If you cannot stand, sit up straight. Your body is your instrument, and good posture is key to achieving a desirable sound and minimizing tension. If you are not used to standing or sitting up straight, this may cause the muscles in your back to become sore over long periods of time. The point is to keep your ribcage and abdominal region in the best alignment for proper breathing.
Practice good breathing habits. Singing requires a large volume of air used in the most relaxed way possible. When you take in a breath, it should go deeply enough into your lungs that the abdominal area between your ribs and belt line should expand. When you release the air you should do so without pushing. To understand this breathing technique, watch a sleeping infant's belly. The belly will expand when the lungs are full and gradually fall as the used air is expelled.
Warm up your voice with at least ten minutes of vocal exercises before attempting to sing anything else. An example of a vocal warm up is to sing an easy starting pitch, followed by a five note descending scale (sol-fa-mi-re-do) on "mmm" "huh" or an easy vowel, such as "a" or "i." Keep in mind that singers typically use the Italian vowel system for vocalization in warm ups: a = ah, e = ay, i = ee, o = oh, u = oo. Trying to sing an ascending scale (do-re-mi-fa-sol) before being properly warmed up can cause vocal strain.
Develop your higher range slowly, paying careful attention to your comfort. If at any time singing becomes uncomfortable, you are doing something incorrectly and should stop before you injure yourself. The quality of your voice in higher registers will likely be different and weaker than your voice in your mid range. This is normal and you should not try to force the volume of your voice to match your middle range. Sing lightly in high ranges, making sure you feel the resonance in your head instead of your chest.
Avoid singing much in the extreme highs or lows of your range very often. Always maintain your comfort level when singing. If a particular song does not suit your range, either transpose the song or choose a different repertoire. Range expansion should happen gradually and always without pressure.