I know it is common sense but you really would not believe the amount of singers who ignore these very simple rules to avoid abusing their voices.

Decrease your overall volume.

Don't shout or yell

Don't whisper! It may actually make your voice worse.

Don't talk in the presence of a lot of background noise! Talk to someone only when they are an arm's length away.

Don't try to talk or sing when you have a bad cold or laryngitis.
 

As a singer you need to ensure that you stay well hydrated. Many physicians and clinicians consider that consuming approximately 64 ounces of non-alcoholic fluids per day is necessary to maintain adequate hydration for the voice Research supports that suggestion that adequate hydration allows vocal cords to vibrate with less "push" from the lungs, especially at high pitches. In addition, well-hydrated vocal cords resist injury from voice use more than dry cords, and recover better from existing injury than dry cords. Increased systemic hydration also has the benefit of thinning thick secretions.

One of the most basic mistake singers make when they start singing is the placement of their tongue.   The tongue is the largest muscle in the vocal tract and to ensure that it does not obstruct the flow of the air as the singer aspirates (releases the air flow), or blocks  the throat, the tongue should always be placed against the lower back teeth when a singer is singing.

Picture of mouth, a singer must be aware of the position the tongue, soft palate and hard palate when singing