For nausea try dried ginger candy, ginger tea (made from fresh ginger), and orange peels or orange essential oils. You put the orange peels in a bag or put some drops of the oil on a paper towel and smell them when you are nauseas. These things worked better for me than Zofran and any of the other aniemetics that were prescribed.
For mucositis try rinsing and gargling (as best you can) with salt water. Do it often throughout the day and follow it with a glass of plain water. Make yourself swallow it (the plain water, not the salt water). Keep plenty of tissues and paper cups around.
For mouth sores ask for a prescription for magic mouthwash (although this won't help if you're really nauseas).
For weight loss try supplementing your food intake, whether it's by mouth or PEG, with body builder's protein and/or weight gain powder drinks. They are available at GNC, most health food stores, and any store that caters to weight lifters.
If you haven't had your teeth removed prior to treatment you must keep them very clean. Brushing them can be a very painful experience especially if you have mouth sores. Get a "baby's first toothbrush" and use that. It is much softer than any adult type you can buy. Don't use an electric brush. You can really damage your gums with one of those.
The best tip of all is to keep your spirits up however you can. If you have a hobby or something that you enjoy doing, try to continue to do it through treatment if you can. Even if it doesn't help your health condition it will greatly improve your quality of life. Remember also that your caregiver (if you're lucky enough to have one) is not having any fun during this ordeal either. Please be kind to them no matter how bad you feel.
Good Luck,
Joe