Practice good posture by standing up straight with feet shoulder width apart. Keep shoulders back and chin out in a relaxed manner. Tension makes it difficult to sing well.
Position arms a few inches from your body so that your lungs can expand. This allows improved airflow from the diaphragm to your vocal cords.
Try this technique of moving your arms to adjust for singing too flat or too sharp. Bring your arms lower to help when you're singing too high, while raising them may aid a too low tone.
Relax your larynx, better known to singers as your voice box, for improved tone. You can feel your larynx vibrate if you put your finger in the indentation below your neck.
Go louder. Often, inexperienced singers have trouble hearing their own voice. If you can't hear your singing you can't correct yourself when you sing off key.
Practice really does make perfect. The more you actively work to improve your tennis technique, the better it will be. Sing anytime you can, whether it's for yourself or others.
Sing with confidence. When you're frightened, your singing voice comes out squeaky. Believing that you can sing well is half the battle.