Stay hydrated. Water helps keep your vocal chords lubricated and protects them from damage, while caffeinated drinks and alcohol remove moisture from your body.
Avoid smoking cigarettes. Smoke and the chemicals it contains do irreparable harm to your vocals over time.
Yell as little as possible to protect your voice from accidental damage. This includes calling across the room or speaking in a noisy location.
Practice singing with a professional voice coach. You will need to learn how to safely and effectively expand your vocal range through proper singing technique and voice drills.
Study the vocals of singers you enjoy and try to identify which vocal quality resonates best with you. Look to reflect that vocal quality in your singing, as long as it does not put a strain on your voice.
Push your voice only as far as you can comfortably go without pain. When you experience pain in your throat, it is a clear indicator you are damaging your vocal chords.