How to surf
From ClanAO Wiki
How to surf:
What is surf?
Surfing is a sort of minigame in TF2. You can only surf on special surf servers, that run surf maps. Surfing is about gliding on sloping surfaces and reaching a goal this way. The maps vary a lot and the goal is not always obvious. Sometimes there's only an arena, where you're free do anything. A lot of of the maps are Counter Strike ports. Some maps teleport you to a "jail", when you fall off a wall. An overwhelmingly beatiful goal room is not always included, sometimes there's just a boring teleporters to the enemy spawn area or to position, where the players in jail don't have a fair crack of the whip to kill you.
Controls
Surfing is done with two buttons:
"Run Left" (Standard: "A" or "Left Arrow")
"Run Right" (Standard: "D" or "Right Arrow")
Do not use "Run Forward"/"Run Backwards". You maybe can to the latter when landing. Also, jumping and ducking is totally unneccassary.
Steering is done by moving the mouse.
To slide on a wall, always walk sideward to the wall.When turning your view towards the wall, you will slide up the wall. When looking away from the wall, you will slide down the wall. If you are not touching a wall and you're just flying through the air, you will also exclusively steer using your mouse and sideward buttons. If you want to fly a left turn, do the same as in normal TF2: Press "A" or "Left Arrow" and move your mouse left, too.
Handy Video
[1] (c)necrodrum