Water
Drinking plenty of water makes a big difference
to singing. You should always drink a glass of water half an hour
before you sing, either performing or practising, & should continue
sipping every 15 minutes. The act of singing causes large amounts of
warm air to pass in & out of the throat, which dries the vocal
folds. They need lubrication, which the body provides in the form of
special mucus, but to produce this there must be sufficient systemic
hydration i.e. more water than you feel you need for everyday
activities. The body doesn't know it is about to have the throat
exposed to drying air, so it can't anticipate the need for extra
moisture - you must help things out.