The first and most important step to surfing is balance, before you can ride your first wave you have to learn to control your balance. Balance is the key to standing up and walking or how you can ride a bike with out falling over. It also applies to surfing is you don't have balance you won't be able to stand up on the board.
We know that there are two force acting on you and your board which is a downward force from gravity and an upward force from buoyancy these two forces are in line and they add to zero and you are stable. Now when you start surfing you will no longer be in a stable frame, you will be accelerating and you will be appling a torque on the board to maneuver the board down the wave.
Picture: by Paul DohetWhen two opposing forces get out of line the board will experince a twisting force, a torque. The board will continue to rotate until gravit and buoyancy come into line again. To do this all you need to do is shift your weight from the center of the board causing the tip of the board to move up, down, right, left.