need to take plenty of water, not to sure about the really hot though, this could do damage your vocal chords as well as iced water.

.Try gargling with a mixture of sea salt and warm water.Honey and lemon in warm water are great as a drink.

keep away from anything alchoholic,the same goes for caffeinne.

Like any muscle you need to warm up.What I try as a warm up is hum, not sing "Somewere over the rainbow" It uses all the notes you will need.
Try and find a key you are comfartable with.

When really bad rest, rest and rest.