Position Surfboard on Wave
When you begin to cross step, you will want to position the board so that it is in the upper third of the wave. The board should be aimed at roughly a 45 degree angle away from the wave. You want to start the cross step while the board is still high, before the wave begins to close out.
Maintaining Your Balance
The key to cross stepping is balance. The more you keep your knees bent, the more stable your body becomes on the board. In addition to having your knees bent, you will also need to keep your head and shoulders up, without bending your body forward at the waist which can easily destabilize you.
Know Which Foot to Start With
Always start the cross step with your back foot first.
Move From Your Knees
The movement that you do with the cross step, moving your back foot over your front foot, should always be done with knees bent. The movement, rather than coming from the waist, should actually come from the knees. Most people's inclination is to rise as they move, but the trick is to keep your knees bent and let the knees do the work. When placing your foot down on the board, you need to really bend the stationary knee until your foot is safely planted on the board. Only when both feet are balanced on the board should you move your other foot.
Practice on the Ground Before Getting in the Water
Much of cross stepping is about how you position your body. By taking away the board and the water, you can concentrate on your body position. The position of your body when you cross step is not a natural position and is one that will need to be learned.
Know When to Cross Step Back
After making your first cross step, you will want to assess the wave again before continuing. If you find that you are going to need to turn the board, or if the board drops close to the wave floor, you will need to promptly step back. Otherwise you're going to quickly find yourself in the water. However, if the board is steady and the wave is still good to keep going, quickly continue cross stepping until you make it to the nose.