"The Complete Ab Program" by Bodybuilding.com and "the Hard 'Core' Abs Workout Routine" Men's Fitness are good full abdominal workout programs. Both programs feature high-intensity exercises and promote consistency and good nutrition.
Abdominal muscles require the same workout approach as any other muscle in the human body. Train with high intensity and overload the abdominal area. Prioritize the abdominal muscles over others, and perform the exercises before training the rest of the body to allocate as much energy as possible to the abdominal muscles. A good diet with a healthy surplus of calories is a must.
The exact shape of your abdominal muscles depends partly on genetics. Even when following the exact same workout routine, different people may have different abdominal structures.