Fruits and vegetables, as well as cereals are considered good foods. In general, foods that are low on fat, especially saturated fat are better.
Anyway, this is a vast subject that can't be discussed in detail here, so you may start by reading some info here (
http://www.nlm.nih.gov/medlineplus/nutrition.html) and you may want to consult your doctor before you make any changes in your diet.
Take care,
