Not to start off doing too much. It’s essential to familiarize your body with using its muscles and learning to breathe properly for swimming. You probably wouldn’t think, but you sweat out a lot when swimming, so make sure you hydrate yourself by drinking enough water. It’s best not to eat too much before training too, in case there’s too much left in your stomach when you get in the pool. Finally, you need to know how to stay patient, because your hard work won’t pay off instantly. Persevere however, and you’ll make encouraging progress.