The right way to pandesal abs (Sourec: http://www.healthtoday.com)

Be careful when choosing abdominal exercises. Some can be ineffective and downright dangerous.

• • Never do sit-ups with your legs held down. It stops the abdominal muscles from getting involved, and the muscles that do get the work out (the hip flexors) put stress directly on your lower back. Instead, your legs should always be relaxed during abdominal exercises and rest on the floor without support.
  
  
• • Never rush through your sit-ups. Fast sit-ups don’t work your abdominals. They may also injure your back because they strain your hip flexor muscles.
  
  
• • Don’t hang onto your neck or head when doing sit-ups. You’ll pull on your neck with each sit-up, leading to neck pain.
  
  
• • Bend those knees. If you keep your legs straight during sit-ups, you’ll only work your hip flexor muscles and not your abdominals.