You can't replace this instrument if it gets damaged!
The fundamental elements for looking after your voice begins with good health. This is very often easier said than done, as many of us suffer allergies, hormonal fluctuations, environmental and emotional stress.
Tip 1. Drink plenty of water. Avoid dehydrating substances such as coffee, anti-histimines etc.
Tip 2. Strive to maintain a physical fitness level. Your vocal folds are like the reed of an instrument and the rest of your body is the "piano accordian" or the power house to create the sound.
Tip 3. REST well.
Tip 4. Warm up gently.
Other nasties to avoid
Smoking - this irritates your vocal folds... not to mention what it does to your lungs. It also stinks!!!! (even smoke machines cause irritation)
Disprin/ asprin - this thins the blood and increases the chance of vocal haemorrhage - nodules.
Coughing - the harshness of the coughing action causes bruising on the vocal folds. Try to sip water instead or swallow.
Alcohol - Although a little may help you to relax, the numbing effect on your chord will make intonation difficult and you may end up singing embarrassingly badly
Yelling - This strains your chords and will cause damage.... use support for projection and relax the throat area.
exercises to try
Homer Simpson says "doh".... change this to a "DA" nice and relaxed. Jaw relaxed.
Without moving your upper body make the DA sound louder being sure not to use your throat at all.... instead use your diaphragm.
Imagine the power for your sound as being connected through the ground and through your legs ... you engage the muscles of your diaphragm and those of your lower back.
Simple things like posture can free your voice and protect it from harm.
The ROCK stance is a great example of gathering energy to support your voice... perhaps a little exaggerated.
Feet should be should width apart, knees just fractionally bent, shoulder down and relaxed. All the throat, jaw neck, shoulder area should be relaxed.