There is not a one size fits all approach to this way of eating. but these are some of the basic ground rules that should give you a head start.
You should try to avoid:
Any grain based food; Bread, Pasta,Cakes, Biscuits,Crackers etc. Also this includes Rice and Corn.
Sugar and anything that has a high sugar content, this can in some cases mean fruit as well particulary if weight loss and blood sugar levels are of concern.
Any processed foods, these probably contain either of the above or both, so if it comes in packaged form it is probably not great.
Any "Junk Food"; Burger and Chips, Pizza, Fried Chicken, Takeaway food, you know the things I am talking about.
Refined oils, Vegetable oils, Canola oil, Rape seed oil, although they have a tag as healthy they really are not they are high in omega 6 throwing the ratio out of balance and they have to go through long chemical processes to make them.
Dairy products, at least for three weeks, this gives you time to notice any potential intolerance's that you may be living with. If you decide to re-introduce Dairy after this time see how it makes you feel, digestive issues or skin flare ups may return.
Legumes, Beans (of all kinds), Peas, Peanuts (peanuts are not nuts)
Base your diet on real food including:
Vegetables, lots of them from as wide a spectrum as you can get; leafy greens. salad vegatables and root vegetables can be included, but not white potatoes.
Meat and Seafood of all kinds.Try to include the whole animal, the offal is a great source of nutrition. Also get the best quality you can afford, free range, wild caught and grass fed being the best choice.
Eggs, one of the most versatile foods, breakfasts, lunch or dinners, snacks and used in baking. Free range as the best choice from a nutritional and ethical point of view.
Fats, from good quality animal sources, Coconut in all forms, Olive oil and Avacados.
Nuts and seeds, all types of nuts are a good go to snack and ingredient in many recipes. Although don't over do a good thing, its easy to throw down a bag of Almonds without a second thought.
Fruit, all fruit but try to avoid the higher sugar containing ones like Bananas, Pineapple and Mangoes particulary if weight control is important to you.
Dairy, if you reintroduce choose good quality and minimally processed. Real butter, cheese and milk can be a great option if tolerated. Choose full-fat varieties as skimmed and fat free are nutritionally void and often have added sugar to make up for flavour.