Cardio is the best fat burner. A good rule of thumb is to do 30 minutes (more or less depending on the intensity).
Try throwing in some HIIT (High Intensity Interval Training) exercises to tone your muscles. These exercises force you to work hard in short intense spurts with little recovery time in between. The result is a spike in your metabolism creating greater after burn (the amount of calories you burn after your workout is over).
I built my HIIT exercises (Core Blast, Sexy Booty, 20x10) from workouts I found here and at ab-workouts-guide.com If you like them checkout Core Abs & Stretches, Sexy Lean Legs, Thankful Thighs, Multi-Plank Challenge, Cut and Chiseled, Mid-Section Drill, or Strong Inner Warrior they're fun and challenging.
Good luck and God Bless!