My experience is that nothing works like cold turkey when it comes to changing habits. So you need to decide that you want to start clean eating and then do it.
Clean your home from everything edible and replace it with good food. Usually my diets fail because I'm hungry and I have nothing good to eat, so pasta it is. If I have no pasta at home BUT I have food that is quick to prepare and good for me, I will eat the good food.
1) REPLACE ALL DRINKABLE WITH WATER
Coffee, tea, soda, juice, milk, wine, what ever it is, replace it with water. It won't be pretty before your brain gets over the addiction to caffeine and sugar and aspartame and what ever, but it will be worth it.
Also, no flavored waters. If you don't want to drink it because it's "boring", you're not thirsty, and you shouldn't drink. It really is as easy as that.
All these "you should drink 2-3 litres of water every day" gurus are wrong.
The only exception is that if you need "sport drink" or some other such, DRINK MILK. No energy drinks or sportsdrinks or other such things. Milk or eat a banana. Or both.)
2) CUT ALL SWEETENERS
You don't need anything more than what is in fruits. No sugar, no raw sugar, no honey, no aspartame, no stevia.
READ THE LABELS!!!
Learn the different names of sweeteners. Like anything "-ose" or "-ol" is probably sugar in some form or another, which makes it a sweetener. (Now, this counts only in ingredients! There is lactose in milk and it's OK, there's fructose in fruits and berries and that's OK, it's only when they ADD lactose, fructose and other -oses in food when it is a sweetener and should be avoided.)
This means that you can't eat cured meats any more. There's sugar in curing brine. This means you can't eat sausage, ham, bacon... (Well... there ARE some varieties made without sugar. Read the labels.)
3) Cut WHITE FLOUR.
Refined wheat is... well, totally useless.
You can cut all grain and cereals. even things like quinoa and the other pseudocereals, to make it easier to stay on the right path, but it isn't necessary.
4) COOK FROM SCRATCH
Try to use ingredients as fresh and unprocessed as you can. No ready-made meals or sauces or mixes and boxes and bags and cans. No freezer meals. No microwave food. The only processed food that is allowed is frozen ingredients, like frozen peas.
6) REPLACE CONDIMENTS WITH SPICES AND HERBS.
Have salsa in stead of ketchup. Add a pinch of mustard powder in stead of mustard. Learn how much you like. It can be potent :-D Most condiments are loaded with sugar, which is on "no-no" list.
You can make salad dressings if you want, as long as you don't use any sweeteners... which makes it sort of impossible to make some salad dressings like mayonnaise. ("But there's no sugar in mayo!" you might say. There's mustard in mayo, and sugar in mustard. So there is sugar in mayonnaise.)
It's easy to make vinaigrette.
1 part of acid (like lemon juice or vinegar (any kind is OK); 2 parts of oil (like olive oil. It must be extra virgin and fresh. If your nose doesn't detect the slightly old flavor, your mouth will. A teaspoonful of fresh olive oil doesn't taste oily. If it does, it's not fresh.)
any extra flavoring if desired. Like salt and pepper, spices, herbs, onion... no mustard.
You can also use sourcream or greek yoghurt as salad dressing. Or cottage cheese. Or a squeeze of lemon. Some vinegar.
7) REPLACE POTATO/PASTA/RICE WITH VEGETABLE SIDEDISH.
You can eat sweet potatoes, carrots, turnips, swedes, parsnip, pumpkin etc. etc. as much as you like. Most potato dishes can be made with these vegetables, and are better for you.
* I am OK with dairy, as long as it's not sweetened. All the cheeses are OK. Read the labels, though. There might be some sugar added to some of this stuff.
* I am OK with fat, as long as it's natural, like butter and virgin oils.
* Use locally produced, organic, ecological, sustainable, small companies, farmers' markets... Go as close to the producer as you can.
* Divide your eating between 6 A.M. and 6 P.M. You can basically eat anything [except sugar (sweetener) and white flour (and other starches)] during that time.
And be kind to yourself. Have a day every month when you allow yourself to eat anything you want to. You can even have a list of "forbidden foods" and then go buy all of it on your "pig day", and eat all you can. Just remember that next day you need to clean out all the left-overs. All of it.
* Find alternative to EVERYTHING BAKED. Like pizza. Sandwiches. Tortillas. Pancakes. Muffins. Cakes, pies, buns, doughnuts, cookies, biscuits, croutons, breadcrumbs, breading...
Your brain is just addicted to the combination of fat, sugar, salt and starch. We are programmed like that. You don't need any of it and will find life easier without them.
If you just HAVE TO get pizza, make a crustless pizza. That is, put all your desired toppings on a plate, put some grated cheese over it, and bake it in the oven as if it was a pizza, and eat it.
Eat a salad in stead of a sandwich. Just put all the meats and whatnots you want on your sandwich in a bowl with some lettuce. It is almost as satisfactory to your senses. If you want some crunch, add nuts. Use a lettuce leaf in stead of tortilla to wrap.
You can use nuts in stead of croutons and breading, too.
* Write a list of 20-30 different clean dishes you like
for every other occasion you find it hard to eat clean.
You can get ideas online. USE them!
THIS IS IMPORTANT
Get a list of foods you MAY eat, not food you may NOT eat.
Buy the house full of good, clean food.
Take some time to make some freezer meals ready that you can just take off the freezer in the morning and have a good, clean meal ready for dinner.
See that you have plenty of things to eat, to snack on, movie snacks, something to nibble - because that is going to be difficult, if you just find yourself wanting something one day and there's nothing snackable in the house. It will end with you wandering off to the closest store and buying some candy and other crap.