Strengthen your core. The stronger your stomach muscles, the more pressure they can withstand. Doing exercises to improve your strength is good preparation for taking a punch. Sit-ups, crunches and other ab exercises that are done on a regular basis will protect your organs underneath your muscles. Because the abdominal muscles support many other parts of the body, it's important to workout the surrounding muscles, including the back and the obliques.
Prepare yourself mentally. If you can visualize taking a punch, it can help to prepare you for taking one physically. Watch the area of the opponent's collar bone because you be able to tell when they are going to hit you, and what hand they are going to use. Breathing out hard and fast after someone punches you will take the air out of your stomach, which will keep you from having the wind knocked out of you. Tighten your stomach muscles to protect your organs and this will also reduce the pain.
Don't panic. This will help you to recover quickly. Don't think about it once you have been punched, as dwelling on it will make the pain worse, which in turn will slow you down. Stay calm and try to go with the direction of the punch at the same time you tighten your stomach muscles. Keep your waist and chest slightly turned, leaving a smaller and harder area on your side to hit. You can also prepare for a punch by having someone pound your stomach with a medicine ball.