do it twice a week to give your abs more time to recover, increase the weight, and do each section (upper, left oblique, right oblique, lower) separately in sets of 12 with a brief rest in between. you should see nice things happening quite quickly.
never mind the "legs out and in" thing - once you open and close your hip joint, your abs move into a stabilizing mode and the actual work is being done by your
hip flexors (not what you want). to hit the lower abs directly, you need to remember that ALL they do is pull the front of your pelvis up - they do NOT move your legs (being as they're not attached to them and all). do reverse crunches instead.
your obliques pull one side of your ribcage toward the opposite hip - do twisted crunches. this will give you a narrower-looking waist.
i personally avoid the side bends (one hand
behind head, the other holding a DB, and bending toward that side) because they widen the waist profile. hanging hip tilts will work those muscles without building them up.
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