If you want to be able to body board, then you should already be a good swimmer. You'll need to use a lot of the techniques you use for swimming to propel your board, and furthermore, you'll need to be a good swimmer to swim without your board if you wipe out. Additionally, you should only try bodyboarding if you know that the sea conditions are safe and that there's a lifeguard on duty. You should try bodyboarding with a friend or an instructor instead of by yourself. Once you get more comfortable with it, you can go at it alone. You'll need to attach the leash to your upper arm. This will prevent you from losing the board when you wipe out. Attach the strap to your upper arm tightly, but loosely enough so that your arm is still comfortable. The leash will keep your arm and the board secured together. If you're swimming in colder water, you'll need a wet suit to keep your body warm. A rash guard will also do, keeping your body from getting irritated while you're bodyboarding, and protecting you from the sun. They are made of Lycra and can also be worn under your wetsuit to keep chafing or rubbing to a minimum. Get some fins with tethers and attach the tethers firmly to your ankles. You'll need fins to help you kick with higher speed, making it easier for you to catch a wave. You should also consider getting a pair of fin socks to wear under your fins, to add an extra layer of warmth and comfort for your feet. Before you try to catch a wave, you should have a strong sense of how you should be positioned on the board. Get in the sand and lie on the board with your hands at the top (nose) of the board, and the back (tail) of the board under your lower belly. Keep your weight centered on the board. Once you're in this position, you can practice paddling. Paddle your hands at the side of the board, like you're scooping water towards you, or as if you're doing the free stroke in swimming. Kick your feet under the water for the best propulsion and faster movement while bodyboarding. Walk into the water with your board until it's about knee deep. Lift your feet high with every step to avoid getting stuck. You should start looking for white water waves that go straight into the beach.
Put safety first. Get a leash. Get a wetsuit or a rash guard. Get fins and fin socks. Practice the correct position. Walk into the water.