Diets
Don't go on a diet. Fad diets may help you lose weight in the short term, but ultimately you are going to gain it all back and then some. Here's why: most diets involve some sort of caloric reduction along with some way to make you not get hungry. The way that it is keeping you from getting hungry is by lowering your metabolism.
This is bad.
When your metabolism is low your body will be much more likely to convert whatever you eat into fat because it will correctly assume that calorie reduction is your intention. Lowering your metabolism is your body's way of keeping an advantage over starvation because fat burns more efficiently over time, and if your body doesn't think it is going to get anything then having a source from which to derive energy (fat) would seem to be a good idea. The alternative is starvation and death. Your body doesn't understand that you live in 2013 and have plentiful food as far as the eye can see.
Make a lifestyle chance by eating better. Going on a diet that you are ultimately going to come off of is going to end up causing you to gain more weight than you started out with.
Drinks
Be aware of what you are drinking. Sugary drinks are your downfall. Most people understand when it comes to sugary sodas, but a lot of people fail to see the other sugary drinks for what they really are: bad. Fruit juices, sports drinks and energy drinks are great if you've just exercised for hours, but for the rest of us we are just drinking straight sugar. Most researchers agree at this point that juices are no better for you than drinking sodas. Make sure that you are drinking water as your primary beverage. A little milk or tea or coffee is ok too so long as you don't start pouring in sugar, but water should be your best friend.
Exercise
Exercise: Your don't have to do 90 minutes of Insanity or P90x, though I certainly would not dissuade you from working out that hard, but a good 10-15 minute interval workout can have equally beneficial results. There are tons and tons of completely free YouTube videos and websites that show different interval training exercises, and most can be done with no equipment, so there is no excuse not to set aside 10-15 minutes of your day to exercise.
If you put together everything above consistently, you WILL be in great shape. There's no getting around it. You really don't have to join gyms, buy expensive equipment, or get into strange fad diets. Drink water, eat six small meals throughout the day, and exercise, and I promise you that you will see results.