Everyone actually has a good set of abs. It's just a matter of removing the fat and sculpting them. In addition, cardiovascular exercise will help tremendously. If anything, you want to do crunches as opposed to situps.
Experts consider situps bad for the back.
Fat is actually burned all over the body during diet and exercise. Sample cardio exercises are the stationary bike and treadmill. If you decide to use a treadmill, brisk walk instead of running. In addition to the above modifications, supplementation of fat burners, meal replacements, and protein can help in most cases. What works for someone else may not work for you.