1. Do not eat or drink sugary substances. This can cause your voice to not be able to function as well. Your voice will not be able to reach its full capacity.
2. Do not eat or drink milk-based substances. This causes mucus to form, which can then result in having to clear your throat or cough.
3. Do drink water. It can help to temporarily clear your throat, and keep it moist.
4. Do drink concentrated lemon juice. Put a few drops in a glass of water, and it will work wonders for your voice.