Eat more fiber

A diet high in fiber (25 to 30 grams per day) reduces the risk of colon cancer, helps to lower cholesterol levels - resulting in a reduced risk of heart attack and stroke, and can improve glucose control in diabetes. 

Plant-based foods provide both soluble and insoluble fiber in the diet. Soluble fiber is found in fruits, vegetables, beans, and grains. The woody stems and seeds of vegetables and fruits and the outer bran covering of all cereal grains provide sources of insoluble fiber in the diet. Insoluble fiber reduces blood cholesterol less than does soluble fiber. Increased soluble fiber reduces cholesterol by binding cholesterol and bile in the small intestine and then carrying them through the large intestine, promoting the elimination of cholesterol and through bacterial breakdown of soluble fiber to compounds that inhibit the production of cholesterol in the liver.

The consumption of 25 to 30 gm of soluble per day can accomplished easily by consuming at least five servings of fruits and/or vegetables and six or more servings of grains daily.  Beans and legumes also provide excellent sources of fiber.

Alternately, psyllium in the dose of 5 gm three times daily (before meals) has been shown to decrease glucose, total cholesterol, triglycerides, and LDL levels, and increase HDL levels significantly.

Eat LESS refined carbohydrates. This includes:

Refined flour

Enriched flour, bleached flour, semolina flour, wheat flour. Examples include: pizza, pasta, bagels, pretzels, tortillas, muffins, breads, baked goods.
Refined rice
Enriched rice, polished rice, rice flour.
Sugar / concentrating sweetners
Anything ending in -ose, including fructose, syrups.

If you are diabetic, your goal should be to eat NO refined carbohydrates.

Eat foods as natural and unprocessed as possible.

The more whole and natural the carbohydrate, the more nutrient rich, and the lower your body's glucose and insulin response.
The more processed the food, the higher the potassium to sodium ratio, which is detrimental to the body in many ways.

Eat non-starchy vegetables

Non-starchy vegetables have more nutrients, are digested more slowly and have a lower glycemic index (explained later).
Examples include: All lettuce, greens, asparagus, bok choy, broccoli, cauliflower, celery, cucumber, green/red/chinese cabbage, mushrooms, spinach, sweet/hot peppers, tomatoes, yellow wax/green beans, zuchini/summer squash.

Eat less natural carbohydrate-dense foods

This includes: whole grains, starchy vegetables (roots: potatoes, carrots), legums, fruits. When eaten, these foods should be eaten with protein and/or fat to buffer the glucose elevating effect.

Do not drink soft drinks, fruit juices or alcohol.

Use olive oil only, not regular vegetable oils.

Olive oil has more omega 3 fatty acids (FA) which results in a suitable ratio of omega 6 to omega 3 FA ratio. It is also low in omega 6 FA and rich in omega 9 FA.
Corn, soybean, safflower, sunflower, and cottonseed oil are all high in omega 6 FA. The current ratio of omega 6 to omega 3 FA in the american diet is between 20:1 and 30:1. This contributes to insulin resistance, diabetes and possibly obesity.

Eat more omega 3 FA whenever possible.

Sources: cold water fish (salmon,trout, tuna) - 2 to 3 times per week. Also, sardines, herring, anchovies, flaxseed oil, walnuts, romaine lettuce, mesclun mixed greens, argula, kale, collard greens, swiss chard.

Avoid trans-fatty acids.

These lead to increased insulin resistance, increase triglycerides, increased total cholesterol, decreased HDL, obesity, and increase coronary artery heart disease.
Examples include: margarine, deep fried foods, partially hydrogenated oils - salad dressings, crackers, breads, cookies, pastries.

Eat protein at every meal and snack.

Protein stimulates glucagon, which is a powerful hormone that opposes insulin (also a powerful hormone). Glucagon allows fat and stored carbohydrates (glycogen) to be burned. The result is a less rapid rise in glucose levels. This is especially important when ingesting carbohydrates during a meal, the inclusion of protein will buffer the rapid rise in glucose.
Good sources: Chicken, turkey, fish, seafood, read meat, lamb, game meat, eggs, low fat cheese (mozzerella, feta, low/no fat cottage cheese). Allow 3-4 ounces per meal.
The best meat is range fed or wild game that have never been given hormones or antibiotics. Eggs should come from chickens fed omega 3 rich flaxseed oil or fish meal.
Alternative sources: Seeds/nuts. These are healthy snacks, protein - mostly monounsaturated fats. Seeds contain the most protein.

 
Adapted from Syndrome X: The Complete Nutritional Program to Prevent and Reverse Insulin Resistance