You don't need to buy expensive exercise machines or join the latest exercise gadget fad in order to work on your abs at home. All you really need are a few basic exercises and the persistence to stick with them until you see results.
You may want to start with classic bent-knee crunches. Lie on your back with your knees bent at a 90-degree angle. Without dropping your chin towards your chest, lift your shoulder blades about 2 inches (5.1 centimeters) off of the floor. Slowly lower your shoulder blades, but not all the way to the floor, and keep your abs tight throughout the exercise to work core muscles. Do crunches every other day, working up to 40 or so per workout.
You can mix these crunches with bicycle crunches. Lie on your back with your knees bent, feet flat on the floor and your hands on the sides of your head. Contract your abdominal muscles as you bring your knees up to a 45-degree angle. Straighten and bend your knees as you alternate crossing and touching your right elbow to your left knee. Then switch and touch your left elbow to your right knee. Do two sets of 10 repetitions (reps) for each leg.
Arm running sounds silly but it helps build up your back and side muscles to balance abdominal strength. To do the exercise, stand erect, hold onto the small hand-held weights and begin moving your arms as you do during running, while keeping your feet stationary. Keep your elbows bent at roughly 90 degrees as you pump your arms. Repeat these motions until you're worn out.
Some runners use only one kind of crunches, along with arm running, as their primary core workout. Others recommend a more extended session including the following exercises:
The plank and side plank maneuvers begin when you lie in a push-up position, but with your forearms on the ground instead of your hands. Hold your body in a straight line and keep your elbows directly below your shoulders. Tighten your abs and hold. Then, shift to your side, leaving the elbow directly under your shoulder and both feet on the floor, with your top foot in front. Raise your hips until your body is in a straight line. Start with 30 seconds and work towards two minutes.
The bird dog is a little simpler. To perform this, start on your hands and knees, with your back straight. Raise an opposite leg and arm to the height of your torso. Hold for 10 seconds and work towards 30 seconds. Repeat the move by alternating arms and legs.
The lunge crunch may help you round out your routine. Stand up straight, and then step forward into a lunge. Try to contract your abs and keep your buttocks tucked under your torso as you lunge forward. Step back into your starting position, and then repeat 10 times. Use the same routine for your other leg.