Stich,
Cardio don't give you abs lah. Cardio uses up energy, which can help burn fat. Rope skipping, jumping jacks, burpees (this is very good), push ups, squat, frog jumps, etc.

Here a good programme:
http://simplefit.org
Explore the website first before you ask questions.
Can work or not? If you follow it and level up, it works very well.

You need to eat the proper way to get rid of the tummy.
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GUYS, I AM GONNA RECOMMEND NOT ONE, BUT 2 BEST ABS EXERCISES EVER THAT CAN ALSO SAVE YOUR BACK!

Sit ups & crunches will give you back pain, sooner or later. especially for people who sit all day long (i.e. fat people, thin people, low level of fitness, students, office workers, myself, etc). They must worry about their buttocks and back. If these people do crunches and sit ups like no tomorrow, they're gonna have back aches in the future.

zOMG!! So what to do now?!

THE 2 PERFECT SOLUTIONS:
1. Start with this exercise: BACK BRIDGE. Whole body from shoulders to knees must be straight like a pencil: no arch, no sagging, no bending, just straight. Hold for 2 minutes, repeat 3x.
http://www.merinews.com/catFull.jsp?articleID=15770653 <---clickety-click!

2. And then this abs exercise THE PLANK (aka prone bridge). Again, whole body from head to legs must be straight like a pencil: no arch, no sagging, no bending, just straight (to prevent back pain).
Do NOT do sit ups after this, unless you want to injure your spine.
Hold for 2 minutes. Repeat 3x.
http://exercise.about.com/od/abs/ss/abexercises_10.htm <---clickety-click!

You can also rotate the exercises whatever way you choose.
After you become FITTER and STRONGER, then go ahead and move on to other abs exercises.

P.S. I'm grinning now, because I know many of you wouldn't be able to complete both these easy-peasy exercises. =P Nyek nyek nyek! If you can complete 2 minutes, please post a video to prove it!

These two are to strengthen your abs and back, and tone up the muscles there. They won't burn a lot of fat. You'll need to eat right and increase energy usage to burn fat.