1. Lie on the floor. Make sure you have enough room to move without hitting any furniture or walls. If you have pets or children, get them out of the way before you start, because once you lie down on the floor, you are asking for their attention.
2. Flatten your back and pull your knees up so they point toward the ceiling with your feet flat on the floor. By pulling your knees up, you are positioning your back so that you do not strain the lower back muscles. You may need to rest here for a moment before getting started on your sit-ups. Many people carry a lot of their daily tension in their lower back and flattening it out may cause soreness until the muscles relax a bit.
3. Choose the position of your hands. There are several options for hand position. Some people prefer to leave their arms down by their sides or place them straight up in the air. Either of these choices makes the sit-up harder to do. They also leave your neck unprotected. The best position for your hands is to hold them lightly under your head but barely touching you. Here you can support your head and neck but the light touch will keep you from pulling on your neck or jerking when you pull your shoulders up.
4. Inhale a breath. Remain with your shoulders on the floor as you take in air.
5. Raise your upper body as you exhale. Pull your stomach muscles in toward your spine so that these muscles are doing the work instead of your back, arms or shoulders. Control the move so that you slowly rise until your back is straight at a ninety-degree angle from the floor. Make sure that as you rise up, your neck is straight and your head remains in alignment with your back.
6. Slowly lower back down to the ground. Inhale as you carefully lower back down. Feel your abdominal muscles contract and use them to control the motion.
7. Repeat the lowering and then rising movement for more sit-ups. Do as many sit-ups as your body feels comfortable with. You should complete ten if you are inexperienced, and as many as fifty if you have experience. When your abdominals start to burn a little, do three to five more sit-ups and then stop.

Sit-ups can be a great exercise for your stomach muscles. When done correctly, you only have to do a few each day to see the benefits.