The abdominal midsection is a primary fat store and is one of the last to be reduced. You cannot "target" fat burning, say by doing abdominal crunches to slim the waist or leg-raises to slim the legs.
The metabolism works holistically across the entire body. The only way to reduce fat is to ensure your calorific consumption exceeds your calorific intake. Diet & exercise like Annwyn said.
However, as it's my day for analogies (hehe!), let me put it this way. If the fat stores on your hips, buttocks and arms are small saucepans, your abdomen is a wok! If you fill them full of fat and do exercise, you'll deplete them all at a similar rate but it'll take longer to empty the wok - that's why your pot belly is almost always the last thing to go.
Now, why is this? Well, storing fat is a survival mechanism - our bodies are basically the same as they have been for a LONG time (long before Subway opened up on the street corner). In days of yore, pre-civilisation and like with all wild animals, storing fat was an essential way to maintain an energy reserve when food wasn't guaranteed to be in plentiful supply.
There's no point storing fat in large quantities on arms and legs, as that is just extra mass to move, which burns more valuable calories...it also would affect your agility. The abdomen is the most energy-effective location to carry fat where it will get burnt the least (yeah, sucks doesn't it) - and that's why the largest fat cell deposits are there.
Liposuction gets rid of the fat cells where it is applied, which means less fat can be deposited in that location. Unfortunately it won't help unless you change your diet because the *same* amount of fat will still be laid down...just in different areas where you do still have fat cells. So, if you lipo your gut and still trough the cookies, you'll end up with flabby elbows and knees.
The conclusion is simple - burn more calories than you ingest and instead of starving, use physical exercise to help raise the burn rate (starving actually promotes fat storage).
Eat more slowly too. There is a surprisingly long latency with signals from an expanding stomach reaching the brain. Take your time to savour each mouthful and you may well find yourself feeling a little fuller earlier. Or, as Jo Brand said, "we get fat because this hole" (pointing at mouth) "is bigger than this hole" (pointing at backside).
