Everybody's different, but in addition to the above, cutting out many highly fatty things(except for a few raw fats like in a piece of avocado, cold-pressed extra-virgin oils, or raw seeds/nuts) refined flour products(especially wheat, as it is a VERY common sensitizer)sugary things, as well as artificially-sweetened things, most dairy and drastically reducing salt in the diet can work very well on flattening that belly, along with solid weight-training, cardio(to burn that layer of fat) and abdominal work(Pilates works on abdominal stuff that traditional exercises often miss). Competitive bodybuilders, who have to strip their mid-sections of fat, swear that diet is 80%of the equation in that matter. You can do the best exercises until the cows come home, but if you are not tightening up the diet, you won't get the super results you want.
An eating pattern featuring natural foods with non-starchy, fibrous vegetables as the main source of carbos in your diet, some whole grain(like brown rice or whole-grain cereal instead of bread)and a bit of lean protein(no more than 3-4 ounces, unless you are on the larger side and hitting the weights very hard)at each meal, along with some low-sugar fruits, is a good base. Yams or sweet potatoes are good too - whole natural carbos. Lots of water is essential - this should be you main beverage - no sodas of any type, diet or otherwise. Eating several times a day is essential too, to keep the metabolic fires going. Whatever you do, DON'T starve yourself to death - just eat enough that you will feel slightly hungry between meals - there's a difference.
This is no easy fix, not the "diet of the week" mentality, but it DOES work. Bodybuilders, models with upcoming photo shoots, as well as film people do this to varying extremes(not all of which are healthy)to get in shape. But or the rest of us, this general plan works very well, because it cuts out the adulterated junk that is causing the problems to begin with! Concentrate on whole natural foods, and bypass the adulterated, processed stuff(as so much has the dreaded high-fructose corn syrup in it anyway which totally sabotages fat loss efforts anyway!) After you've gotten to be where you want to be, you can loosen up a bit on the diet, but still keep it natural and low in sweets and flour stuff.