The main problem with surfing, apart from the fact that it is almost impossible, is that you get sand in your wax, which turns your board into a manually operated belt sander, especially as you duck dive under waves. This is not such a problem in cold places, because you wear a nice long wetsuit. But in warmer spots, your legs/knees with soon resemble a raw souvlaki column. This instructable tells you how to clean the old wax off, and put new stuff on!
Step 1: Start with clean board
Step 2: Waxing
Choosing your wax!
There are all different kinds of board wax to suit different water temperatures. Where I live, the water is about 22C at the moment, so I use Sexwax 3x cold water soft "Quick Humps". I'll leave that there. There's a big difference in types of wax, in warm water you want thicker wax, in California you can just about dip your board in diesel and have it wax up. Ask the surly guy with his pants halfway round his arse in the surfshop what to use for your local area.
Now, rub the block of wax across your board, and then lengthways over the same area. Pay special attention to the rails - it's not considered 'cool' to have lots of wax on your rails because in theory it cuts down your speed on the wave. However, this is like worrying about the wall paper on the space shuttle. The only people who are good enough to notice a reduction in board speed have an army of groupies to wax their board for them. For regular surfing mortals, wax on the rails means you can hold and push the board down for duck diving - if your hands slip off during this process you cop a board in the face, 'Sticky rails to you, till we meet again' etc. So: sticky rails is nice rails.
A note on board wax: There are good places to keep board wax and bad places to keep board wax. The dashboard falls into the second category. See pic.