Surfing is a sport of constant change. Every day the ocean presents a new challenge. Different swells, crowds, wind and other conditions make surfing the most difficult sport to improve quickly. The number #1 best way to improve is by repetition. Surfing every day helps build muscle memory and timing, which I feel are the two most important aspects of surfing.
Surfing is a sport based on finesse. It requires good body mechanics in order to maneuver the board. This is why flexibility is so important.
Work with a coach
Find a coach in your home town or even just reach out to one of the local rippers at the beach you surf at. This can be a game-changer for you. The sooner you know what to work on, the quicker you will improve.