it may sound silly but get a gym/work out buddy. having someone depend on meeting you or going with you will keep you in check. And then you could push and motivate each other.

well the only reason which can help u in loosing weight i suggest stop drinking sodas,drinks eat healthy stop heavy and junk food. stop eating heavy after 6 pm. and eat as the size of your palm...make this your regualr habit and on the other side jus start som exercise for example say jogging or walking 30-40 mins a day ....i bet u will notice yourself within 2 weeks....good luck...
idont recommend spending money on diet foods and gym and all the stuff.

Well that's about it really. Make sure you keep track of what you eat (I prefer this counter: http://caloriecount.about.com/) so that if you do slip up you can see why and come up with a plan to prevent it from happening again.
Donate your "fat clothes" as soon as you can wear a smaller size. It's great motivation to stay thin as you don't want to go buy bigger clothes all over again.
Take lots of progress pictures of yourself as you go. One per week. You may not see the change as its happening, but I guarantee that if at the end of each month you look back, you'll see it.