A great aerobic workout that can be done in a group setting is step class. Normally 30 minutes to an hour long, a step class can help you build cardiovascular endurance while helping with your blood circulation and allowing you to burn fat.
This means that not only will you lose weight from your body frame but inches as well. The scale and your appearance will both improve as a result.
A good pair of supportive shoes is a must for a step class, as the repetitive motion can cause stress on your knees and ankles if you don't wear good sneakers.
The gym or fitness center you sign up with should provide the equipment, which consists of a small bench with special grips on it and sometimes a small mat like you would use for yoga. Other than that, the only other thing you may find in a step class would be some music to help set the tone and pace as you workout.
There are some very basic moves that your leader will show you at the beginning. Once you have mastered these (which is very easy to do) then you are ready to proceed. This makes it a great workout for newbies and seasoned exercisers alike, since nothing is particularly complex about it.
This type of program is done 3-4 times a week and should be incorporated with some strength or cross training as well for a full body workout. Many people in fact alternate this with weightlifting or other strength-builders.
As you get better, you may want to add levels to your equipment platform, though this is best discussed with your leader first.