i know a lot of other people have put their input into this... many people are saying right well known things but aren't necessarily putting everything out on the table at the same time
as mentioned before, you can't lose just stomach fat. there is no such thing as spot treatments unless you do surgery.
the only way to really lose that fat is to do a caloric deficit and basically lose weight/fat. now some people can lose a lot of fat but maintain their weight through weight lifting and cardio (basically changing their body composition to a low fat percentage with higher lean mass percentage and gaining muscle), but this is really really hard to do...
so what should you do? well for one thing i can tell you that i don't have a six pack. my core is pretty strong but the six pack is more of a long term goal and not really an immediate concern... but there are a few things that have been discussed before that can definitely help you.
1. eat clean
2. drink water
3. space out meals
4. lift (perhaps more core requiring lifts) + cardio
there's plenty of info out there as to what to eat/when to eat/what exercises to do... you should read up on them. more than likely some of the suggestions will not work for you, so you keep searching until something works. my 40 pound loss was from weight training and running twice a day for 2 1/2 months before college... but you probably won't have that kind of time... so just search around for things that will work for you
if you are ever in the gym and you see these http://www.fitter1.com/Assets/Product/Product/GH.jpg
lying around... you should try em. one of the best exercises i have ever done for my core is supersetting "mountain climbers" with a plank hands-walk.