We recently vacationed in Maui, and at the top of our list was taking surfing lessons. We weren't sure what to expect, and our instructor was very patient and reassuring. We were given multiple briefings while still on dry land, and we started out in pretty shallow areas of the ocean. It was nice to be able to surf with a group of beginners, and everyone was very supportive!
What we enjoyed: the expert coaching and the aqua photographer who took photos of everyone surfing.
Some of the things I wish I had prepared for: Listen closely to the tips, especially those on how to fall. You have to constantly be on your alert out there.
Tips: Use the facility restroom (ask for their private key) before you leave the surf shop. Do not bring any valuables with you, including cell phones nor sun glasses. I don't recall seeing any lifeguards out there on the beach, so for the most part, you are on your own.