To work the flab off, do some cardio like the guys said:
The optimal work-out schedule is to do your cardio first thing in the morning when you wake up...drink about 16oz of water, don't eat anything, and then go to town. IF you know how to workout you only need to do cardio for about 15-25 minutes. Check some good fitness sites or look at some of the training books recommended by places like "track and field news". After running or whatnot, don't eat for about 30-60 minutes, and then give yourself a high quality protein meal.
For your abs...work them like you would any other muscle. I laugh at the people who strain in the gym to something like 5 sets of 100 crunches. Think about it...are your abs muscles any different from any other muscle group in your body? NO. So don't blast them with low resistance high rep sets.
I do my abs in a pyramid. Here's what to do (rest only about 45-60 seconds between sets unless otherwise noted):
set #1 - crunches on a flat bench, do about 12-20 or so...don't exhaust yourself
set #2 - 10-12 reps on a crunch machine, set the weight so that you could do about 20 reps if you wanted to
set #3 - 8-10 reps on crunch machine, set weight so you could do about 14-16 reps
set #4 - 6 reps on crunch machine, set weight so that you could do about 8 reps
set #5 - 12 reps on crunch machine, use same weight as in set #3, do not rest afterwards, go straight to set #6
set #6 - 12+ reps on crunch machine, use weight from set #2...try for 12 reps but keep going until muscle failure.
Your done! This simple routine is very quick but burns like crazy on sets #5 and #6.
Does this work? Well, I do this once every 3-4 days with my leg work out (been doing it about 6 months or so)...the "clefts" between the muscles of my eight pack are about 1/4-1/2" deep so my abs are pretty ripped and my gut is also extremely strong which has vast improved my all around strength and speed. MY rib cage muscles are also pretty cut.
I think I'm around 8-10% bodyfat but I don't really know. Also, sometimes I run twice a day for about 20-25 minutes each time, morning and evening, or I play basketball in the evening every now and then.
And don't forget, proper nutrition is paramount to building a healthy fit body. That is a whole other story; anyone who wants to know a little about it, feel free to PM me.
Just trying to help!