• Lay flat on your back with your knees up and your feet flat on the floor, as if you were getting ready to do a sit-up.
• Lift your head and shoulder blades off the floor in a sort of “mini-crunch.”  Your abs should be contracted.
• Place one hand on your belly, just below your belly button, and press down slightly with your index and middle fingers.
• Move your index and middle fingers side to side.  You should feel two harder ridges of muscle on either side of a softer space in the middle.  If you can move your fingers more than two finger-widths side to side, your abdominal muscles have separated.

If you find that your abs have separated, start out with gentle exercises such as these, developed especially to remedy abdominal separation, by Lisa Stone, ACE:

• Lie on your back with knees bent and feet flat on the floor. Place your hands on your abdomen with your fingertips pointing down toward your pubic bone. Exhale as you slowly lift your head and shoulders while pressing down and in with your fingers.
• Take a long towel and wrap it around your torso with the ends in front. As you do a crunch, pull the ends of the towel towards each other in front of your belly button.
• Lie on your back with knees bent and your feet flat on the floor. Exhale and slowly extend one leg along the floor, feeling your abdomen contract below your belly button. Inhale and return to the starting position; repeat with the other leg.

Once the gap in your abdomen is two finger widths or less, you’re safe doing more advanced exercises to tone and strengthen that area.