Know what causes vocal blowout. Some external causes are poor nutrition, alcohol, smoking or being exposed to secondhand smoke and not getting enough rest. The biggest internal cause is straining the voice, which can be prevented.
Prepare the muscles of the vocal cords for intense use by warming up, just like you would any other muscle of the body. Vocalists do this by singing scales, starting softly and in a comfortable range of musical notes, gradually moving to higher and lower notes, which are harder on the vocal cords to sing. It's also important to warm up the muscles of the mouth and face.
Keep your throat well hydrated, not only when you're using your voice strenuously, but at all times. This will prepare your voice and keep it in top condition for when it's going to be heavily used.
Rest your voice if you feel as if it's being strained. Singing through vocal discomfort on a regular basis leads to more serious conditions of the throat such as polyps, which need medical intervention, and have been known to end singing or speaking careers entirely.