The best thing you can do is eat healthier.
Smaller portion sizes- Wait 20 minutes then see if you are still hungry enough for seconds.
Skip the desserts- There is no need to have ice-cream and cake every night. Try having an apple or a cup of jello or pudding.
Snacks- Opt for a piece of fruit, cracker with peanut butter, nuts, or slice of cheese instead of chips and candy.
Once you have your diet under control then make sure your getting a nice burn.
Cardio is a great!
Running- It doesn't require special equipment (except some quality shoes)
You can can do it just about anywhere
It's high impact, which helps build strong bones and connective tissue
It gets your heart rate up more quickly than low or no impact exercise
It helps you burn serious calories, especially if you add hills, and/or sprints.
Jumping Rope- A 145-lb person can burn 330 calories with a 30-minute workout, but you'll want to slowly work your way up to that.
Start by jumping for 1-2 minutes at a time, taking breaks by marching in place and swinging your rope in a figure eight motion. Continue alternating for 10-20 minutes and, over time, gradually increase the amount of time you jump while decreasing your rests. You can add variety by trying different foot patterns (jumping on one foot, scissor jumps, etc.)
These are two of the best and easiest things you can do...