Exercises for a Flat Tummy

Crunches using an exercise ball are very effective.
Place the ball on the floor and sit on it keeping your feet on the floor.
Roll the ball further back so it supports your lower body. Lay back until your body is parallel to the floor.

Contract your abs, place your hands under your head and raise the torso until you reach a 45º angle. Lay back again and repeat several times, keeping your feet apart and after that pulling them closer together.

For the bicycle exercise you need to lay back on the floor and lift one of your legs just as you would be standing on your knee.
Place your hands under your head and touch your right elbow and your left knee, then switch to left elbow, right knee.
Keep alternating the legs just as you would be pedaling on a bicycle.

Do these exercises for a flat tummy on a regular basis to get the results.