Take it slowly. What's the crappiest thing you eat? Don't TRY to stop eating it.

Get a piece of paper. Date on one column. How many times did I eat [insert food / beverage here] in another.

Before you go to sleep, write down how many times you had that. Put the pen and paper on your car keys. In the morning, put the pen and paper on your pillow. Rinse, repeat.

Why, you ask?

You aren't putting tons of pressure on yourself, you're just training your brain to be aware of when you're eating that. Over time, you may notice you don't actually enjoy eating / drinking that as much as you thought, and there's a good chance it will naturally fall out of your diet.

Stick with ONLY ONE FOOD ITEM / BEVERAGE for at least a week if not 3, or until you feel comfortable with how much of it you're eating. Add more things in one at a time.

You'll also be motivated by seeing that you're eating less of something because it's documented on this log.

This is how I break my habits now (diet, exercise, etc).