First, eat everything as close to how it comes naturally. Avoid prepared and packaged pre-made foods.
Two guidelines for each meal: what and how much
Half of every plate should be vegetables. Best to have a couple of different vegetables. And for this classification, they do NOT include potatoes or corn as a vegetable.
Eat as wide a variety of vegetables as possible, including: lettuce, kale, spinach, chard, onion, carrots, green beans, peas, squash (any type), sweet potatoes, celery, tomatoes, bell pepper, beets, turnips, rutabaga, cucumber, broccoli, cauliflower, cabbage, brussel sprouts, I like to make a stir fry out of 4-5 veggies, giving me a full range of nutrients (I do not make a sauce ... sesame oil and soy sauce and fresh-ground black pepper provide the flavors).
One-quarter of every plate should be protein in some form:
For meat eaters: Lean meats (poultry), seafood (salmon at least once a week for the Omega-3 content).
For non-meat eaters: Legumes (the seeds of any of the varieties of beads: black beans, garbanzo beans, soy beans, lentils, etc), low-fat milk or low-fat cheese, nuts, seeds, quinoa, eggs.
One-quarter complex carbohydrate:
Corn, potatoes, whole wheat or whole grain pasta, whole wheat or whole grain bread.
Fruit for snacks.
Avoid butter ... use olive or sesame oil instead.
Avoid factory-made, prepared foods.
Avoid fried foods.
Avoid foods with while flour and/or sugars in it (and sugars include honey, sugar, brown sugar, any ingredient ending in "-ose", corn syrup, etc).
Avoid soda pop and alcohol.
And choose whole fresh fruit over fruit juices.
Drink 6-8 glass of water a day.