When shopping for food, try to stick to the perimeter; or around the edges of the store. This is usually where the fresh produce is, as well as the meats and dairy products. These are the things to stick to in a healthy diet. By sticking to the perimeter, you'll only buy things that support a healthy diet.
Even if you're not a vegetarian, you can improve your nutritional profile by having a vegetarian meal 2-3 times per week. It will help you to learn about other foods besides meat that contain protein and how to incorporate them into meals.
Sometimes people fail when trying to lose weight because they allow themselves to get so busy, and don't have the time or energy to cook anything. Make an emergency kit for times like these that is filled with healthy foods like nuts, fruits and veggies. Take that with you wherever you go, and if you are hungry you will have something to eat that does not include a drive through and extra pounds.