1. Soda. Soda is packed with calories and contains no vitamins or minerals. As soon as you're done drinking one, you'll go for something else since it doesn't keep you full for long. A good alternative to soda is water. It will keep you full without any calories. If you don't like water, try drinking a fruit juice made from real fruit (check the nutrition label for any added sugar). While most fruit juices are high in calories like soda, they also contain some nutrients.
2. White Flour. Refined flour is used in white breads and many baked goods. During the refining process most of the vitamins, minerals and (most importantly for a diet) fiber is taken out. Food with fiber will keep you full for longer. Whole wheat breads have the same amount of calories as white breads but when you eat them you'll stay satisfied.
3. Fast Food. Fast food is loaded with more calories than you'll ever want in one meal. For some people, the calories in one meal is the amount they should have in an entire day. Instead of eating fast food, start cooking, making your own lunch or finding a healthy snack that will hold you over until the next major meal.
4. Candy. Candy has the same problem that sodas have. They are loaded with calories but have little or nothing in the way of fiber,vitamins or minerals. Since candy is made out of mostly sugar, it's digested very quickly. Even if you eat a large amount in one sitting, you'll get hungry very soon which will cause you to eat more throughout the day. This will throw your diet off coarse through an increased caloric intake.
5. Foods You Can't Stop Eating. Avoid any food in which moderation isn't possible. Even when we're on a diet, we still need to enjoy our food. Sometimes you need to satisfy a sweet tooth and that's fine. The problem comes in when you just can't stop eating a food. If there's a food that you can't stop eating until its gone, then avoid it. You can gain weight off of anything, even healthy foods. Moderation is very important.