Are you spending hours doing  sit-ups that aren't really having that much effect?  Choosing smart ab exercises will save on gym time as well as frustration.
Here are some tips to start chiseling your six pack abs.
Growth You'll see faster gains when you focus on movements that reduce your balance.
Performing exercises that reduce your balance  will require using your entire abdominal core.
Stop doing regular sit-ups, you're not working your core.
 Exercises The one legged squat, one arm shoulder presses, or bent over dumbbell rows while balancing on one leg  creates an unstable surface.
These are great exercises to perform at home.
All you need is some free weights and discipline.
The secret exercise for abs is the "hanging leg raise".
To perform this exercise properly you'll use your lower abs to rotate your pelvis (rotating the pelvis is the key to this movement).
You also have the lying leg raises, which are excellent for building up your  core.
Weights You'll increase muscle mass when you add weights to your ab workouts.
  Increasing  muscle mass also increases metabolism, which can indirectly burn body fat.
  So adding  weights can increase strength, decrease the risk for injury and burn fat.
The Right Routine Knowing  when to do your ab exercises depends on your over all goal.
Your want to ensure that your abs are as fresh as possible when working them.
For Performance  - do them on a separate day from all your other work.
To Build Strength - do them at the end of your workout session.