1: The muscles of the core are for posture and movement of the spine, not just for show. this means when you train the muscles you should train all of the various movements or train the core as a whole.
2: Learn how to Engage the core to make your exercises more effective.
3: effective ab training to improve appearance is a form of bodybuilding and so certain protocols should be followed to ensure success.
4: No amount of ab curls and trunk rotations will make up for a poor diet. its the most important factor.
5: More is not better, practice quality over quantity and ensure you actually feel the muscle working.
1 The abdominals are to maintain posture and aid movement - not just for show.
'The abdominals' are made up of the rectus abdominus (abs), external oblique, internal oblique, transverse abdominus and work together with many other muscles such as the erector spinea, the psoas muscles.
The muscles are working constantly especially when standing or carrying something to maintain balance and correct posture.
The muscles combined are capable of flexion, extenstion, roatation, hip flextion, stabalization and more.
For this reason it is important that any exercise programme is balanced and doesn't over work one muscle group over another, this can cause injury and postural problems. Try to alternate flexion (crunches) with extension (dorsal raises) , rotation (trunk rotation) & side flexion (side crunches and oblique curls). And incorporate stretches to maintain flexibility.