The best way to get good abs is to do sit ups, lots of them and different types. Twists, full sit ups, half sit ups, legs to the side sit ups etc. Leg raises are also very good at toning the stomach but make sure you do them with your legs dead straight and not bent, I see so many guys at my gym who after about 10 decent leg raises start bending there legs and it means you are not getting the full work out. Also get yourself a medicine ball, I have been using a 7kg ball for about 4 months now and although it can be painfull I can really see the difference and feel the difference when I get hit with a body shot in the ring.
Its probably easier for me because I am about 6ft in height and weigh about 11 stone but the only way to get good abs is through hard work and its took me about 10 years of hard training to get my six pack to what it is today. But believe me its worth all the hard work when people especially Ladies comment on it in the summer!!!