bad form can lead to injuries
the reason why majority of people at the gym who have a regular fitness schedule dont see there abs is due to fat. Most people have large fat deposits in there midsection on top of there muscle. Thus they can have a perfect six pack under their belly. This is often the case with football linemen who can spit out 200 straight situps but dont have a pefect 6 pack
bottom line if you want to show your abs, eat right (
high protein,
low fat, good carbs) lots of cardio to shed the pounds, and work the abs. Core strenght like welch said deads, squats and situps help the most.
follow that routine for a few weeks and your should see some progress