There are a few things that, if they're in the top five ingredients of a type of food, you should avoid, particularly if you want to lose weight;
Enriched flour (any type); for the reasons that disgruntled said above.
High Fructose Corn Syrup; This stuff is instant energy. It takes nearly no energy or time for the body to turn HFCS into energy, and, therefore, fat.
Hydrogenated/Partially-Hydrogenated Oil (any type); Not so much for weight loss, this stuff stays in the bloodstream for years, making it a severe heart risk.
Keep cookies, chips, soda, and other junk food out of the house. Instead of cookies, healthy muffins (or, if one is inclined to cook, cookies may be made out of healthy things like soy flour and flax seed. My mom has gotten really good at making healthy sweets), instead of chips, a good grainy cracker like triscuits (they make some great flavors, like garlic herb), instead of soda, bottles of tea (either unsweetened or sweetened with crystalline fructose), or Smartwater (I love this stuff) or unsweetened flavored water (my favorite brand is called Twist, I think).
Do not try to deny cravings, just make sure you're eating healthy when giving in to them
It is important to note that there are more and more studies coming out that suggest that artificial sweeteners do not lower fat gain or speed weight loss. These sweeteners technically do have calories, and it is believed that they put the body into energy-storage mode just like regular sugar.
And, as disgruntled said, activity is a must. Start small, like parking at the back of a parking lot. If you work in a cubicle, stand as much as you can while talking on the phone. It may look odd, but it's good for you.
Edit: I would personally stay away from diet pills, as disgruntled said. If you are going to go the medicine route, talk to a physician about it. There is only one OTC med that is actually verified by the FDA (US, of course, unsure of other countries) to safely aid in weight loss. There are other, prescription drugs, as well. Please do not go on any of these without talking to a physician.