This one is tough and might take experimenting with several techniques shared here. The most important thing is to keep trying until you find a system that works for you. I happen to enjoy eating out myself and can occasionally fall into this habit. So here's my approach.

I keep a small baggie of nuts like n my pocket or backpack. There are tons of varieties and flavorings to choose from. A handful is good at satiating your hunger and meets the boredom piece. It's like reaching for gum instead of a cigarette.

Second, when I fall into the habit of eating out I start using cash if I can. If I make it through the day without buying anything I put 15 bucks in a clear jar on my dresser. At the end of the month I treat myself to something I want from one of my hobbies.

More than anything though you have to work on changing your body chemistry. Eating right at home is essential to this. Stock up on food that is as close to it's natural state as you can. The first month of avoiding sugar and fatty fried foods is awful. Your body is litterly addicted to this stuff through millions of years of evolution. You have to have a meal plan, including making a list before you go shopping and sticking to it.

If you are out and need to eat think about where you're going. Obviously avoid corporate death burgers and fried food. Salads with grilled chicken are your friend. Leafy greens are highly filling and filled with good micro nutrients that will help you move on from the fat and sugar addictions.

Try to change your perception of food. It can be a social, joyful thing, but if you look at it as a fueling cycle it changes what food's purpose is. Pick up an active hobby that requires solid eating habits to fuel.

Finally, if you aren't perfect, don't worry about it. Just note it and move on with the next meal. Do not fall into a place of self loathing if you cheat a bit.