Everything that grows naturally (vegetables, fruits, nuts, grains, seeds, etc.) is good for you. Try eating them mostly in as natural a state as possible (baked, steamed, boiled, lightly sauteed, etc.) and limit cooking methods that destroy their food value (deep frying, over-cooking, etc.) Use whole grain products rather than refined flour.
Limit your intake of stuff that's manufactured for you (biscuits, chips, frozen dinners, etc.) especially those that have high sugar content (jams, sweetened juices, soda, chocolates, sweet cereals, etc.)
Reduce your sugar and salt intake.
