If you try to eat most of your meals at home, where you can get good, fresh ingredients, you won't be tempted by fast food. Most fast food places don't have any "good" choices, but they do have some that are better than others, so if you find yourself having to do fast food, make sure you're making the best choice possible - that doesn't include a double cheeseburger and fries...
If you do go to a fast food place, get a burger with lettuce, tomato, pickle and onion, no mayo... ask for a knife and fork, then remove the bun and eat the meat and veggies like a salad. Still not a good choice, but better than the double cheeseburger.
Also, being prepared by having something with you to snack on will help keep you out of that drive through.
Food is like an addiction, you have to stop but not immediately. You should also realise what you are actually eating...
A great way for me to cut down fast food was to always have a bottle of water with me and some healty snacks. That way I know I have food with me and I dont have to spend extra money on unhealthy food.
The problem with fast food is that it isnt helping you to get rid of the "Im Hungry"-feeling.
Fruit is almost alway a Fast Food, just grab an apple and off you go, its simple as A B C