You should try and cut out dairy produce if you can - particularly milk and cheese becase they stimulate (sorry about this!) mucus production in your system.
Try and keep away from smoke, drink a lot of water, and basically eat a healthy diet and get good exercise and sleep.
The voice is just a part of the body, if you maintian the whole thing, then your voice will benefit.
If you don't have training, try and get some diaphram exercies - a book or tutorial on acting and voice projection will belp you to use your diaphragm rarther than sing through your throat wihich will wreck itself in about two days.
Hope this helps.