Control your diet by eliminating caffeine, alcohol, smoking and reducing dairy intake. Caffeine and alcohol dry out the vocal cords making them less resilient. Smoking may limit your lung capacity. Avoid dairy products within hours before singing as they create excess phlegm that will interfere with proper vibration of the vocal folds.
Stand up straight when you sing and breathe from your diaphragm. Carefully monitor your body for any tension in the neck, shoulders and jaw. Tension will prevent your vocal folds from vibrating which reduces the amount of vibrato in your voice. Vibrato is the natural characteristic of good vocal technique producing a characteristic wobbling of the voice.
Sing a warm-up as part of your daily practice routine. A good warm-up consists of long tones and scale exercises to increase your tone production. Sing chorales in the middle of your range and avoid any music that extends too high or low during the warm-up.
Practice appropriate singing exercises to extend your range. One excellent exercise involves singing "hmm" on a pitch near the middle of your range and extending down a perfect fifth singing each diatonic note in between. Diatonic notes are the non-chromatic notes found in a scale. For instance, C, B, A, E, F are all diatonic notes. Continually increase the pitch by one note at a time until you have reached the highest comfortable pitch in your range.
Enunciate words and study diction to ensure that the words pronounced are clear and articulate. Diction will teach you the proper way to pronounce syllables and words in every language. It uses an International Phonetic Alphabet (IPA) to help you quickly learn to pronounce words properly.
Read music and practice repertoire from famous operas, arias and songs on a daily basis. A private instructor will help you to select songs that fit your vocal range and will help to improve your technique.