Good looking abdominal muscles rely more on your total body fat than on the exersizes your choose. You can do leg raises, pikes, and weighted crunches until you vomit, but without a reduction in bodyfat you will simply be spinning your wheels. This being said, focus on your ENTIRE body at the current time. Start with a resistance training routine filled with compound movements, and work at getting stronger in the 8-12 rep range. Combine the routine with a clean diet and you should be on your way to an improved midsection.