Basic strength in the stomach can be developed with following abdominal exercises. Start by aiming for 1-3 sets of 10 repetitions three times per week and gradually build up to 20-25 repetitions.
Static Contraction
1) Lying flat on your back bend your knees bent so feet are flat on the floor.
2) Contract your stomach muscles and try to push the small of your back into the floor.
3) Hold for a count of 5 seconds remembering to breathe gently. Relax and repeat for the desired number of repetitions.
Keep your neck and face relaxed. Many people have a tendency to hold their breath during this exercise which can increase blood pressure.
Wrist Ups
1) Lying flat on your back bend your knees to right angles keeping your feet flat on the floor.
2) Place your palms on your thighs and sit up until your fingertips reach your knees as you breathe out. Return to the start position and repeat for the desired number of repetitions.
Imagine you have an apple under your chin. That's about the distance your chin should stay away from your chest during the movement. 
Oblique Crunches
Abdominal exercises such as these emphasize the internal and external obliques rather than the rectuse abdominus and transverse abdominus.
1) Lie flat on your back, knees bent at right angles and twisted to the left.
2) Place your fingertips to the side of your head just behind your ears.
3) Curl up just enough to lift both your shoulders off the floor a few inches.
4) Hold that position contracting your abs as forcefully as possible as breathe out.
5) Repeat for the desired number of reps before to switching to the other side.
Supermans
This is not technically an abdominally exercise at it works the lower back.
1) Lie on your front with arms outstretched over your head, palms on the floor.
2) Simultaneously raise your right arm and left leg off the floor about 6 inches keeping them extended.
3) Hold for 5 seconds and repeat with the opposite arm and leg.
4) Repeat for the desired number of repetitions.
from: www.sport-fitness-advisor.com
Posted in: Exercise