Successful people usually have an important common trait--a clear and strong voice. A good voice isn't just a necessity for performers, it is a crucial component in business, social interactions and relationships. A confident voice is often enough in itself to enroll others in what you are communicating. A weak voice almost will certainly undermine your intended self-expression, no matter how articulate you are. Learning to stop your voice from changing when you are nervous will facilitate the powerful pursuit of your goals in life.
Breathe. Nervousness makes your heart beat faster and adrenaline floods your system, which will in turn bring on a change in your voice. Your body and brain need extra oxygen in high-stress situations, but nervousness will often cause short, panicked breathing. Controlling your breath is the bedrock of a powerful voice and a controlled body. Take deep, slow and full breaths. As you inhale, expand your abdomen and lower back instead of only your chest. This will slow your breathing, give you a full tank of air and prevent you from hyperventilating. Breathe in through your nose and out through your mouth. Making an "ooh" shape with your lips as you exhale causes your air to come out in a steady, controlled stream--just as you will need for speaking.
Warm up your voice. Your vocal cords are like any other muscle in your body--if you use them strenuously without stretching them a little first, they won't be as responsive. Worse yet, you can easily tire or injure them. Warming up can be as simple as humming quietly to yourself as you slowly inhale and exhale. Pick a note low in your "register" (your normal range of comfortable speaking) and hum it for a few seconds, then slowly slide your hum up through your range to a comfortable high note and back down again. Do this a few times to get air moving over the length of your vocal cords. Warm up your mouth, lips and tongue, too. As you hum, gently stretch your jaw forward and down like a yawn. Move your lips in and out of different vowel shapes (e.g. "ah," "ee," etc.). Stick out your tongue all the way, then all around inside your mouth. Finally, "buzz" your lips (let them flap as you pass air between them) and roll your tongue on an "r" sound.
Know what you are going to say and how you are going to say it. If you are preparing a speech, practice it several times to become thoroughly familiar with its structure. Support this structure with strategically placed deep breaths or short pauses. If you are speaking in normal conversation, take your time and use your breath. Breathing fully before you speak gives you a great opportunity to collect your thoughts and articulate them clearly. Furthermore, controlling your voice often can translate into controlling a conversation; an even temperament might lend you an air of authority and conviction.
Maintain good posture. Slouched posture interrupts your air flow, and rigid posture doesn't allow you to take in a full tank of air. Relax your shoulders and expand your chest by gently squeezing your shoulder blades together. Stand with one foot slightly behind the other and don't lock your knees. Keep your chin level and your neck straight.
Speak on your breath. Say your words in the same comfortable low register and with the same amount of air behind them as in the humming warm-up. By keeping your breath controlled and your vocal cords relaxed, you easily can stop your voice from changing when you are nervous.
Enroll with a vocal or self-expression coach or join a speech-making organization. They can help you master the art of expressing yourself. Practice speaking with your friends and loved ones to get comfortable. Remember that people are certainly rooting for you to speak well and that everyone gets nervous just like you.