Follow these tips and start progressing today!
Training
A sport this complete requires that you give it your all, every single day. If you don't have any sports background, then start by weight lifting and building up strength. Next you can enter the world of gymnastics and eventually complement these two areas with endurance training. It's gonna be a tough ride, but well worth it.
Nutrition
There are plenty of diets to choose from: Paleo, Zone, Atkins, etc. They are all valid, as long as you can adapt to them and get results. A simple yet effective rule is to eat clean and stay away from processed foods.
Supplementation
Absolutely fundamental! When practicing a sport this intense, you'll need all the "help" you can get. Using the right supplements can determine whether or not you'll manage that one more rep in your WOD or finally improve your 1RM. So eat well and supplement yourself even better.