How to Surf in Counter-Strike SourceFind a surf server. If there's none around when you look, download the maps yourself and load a LAN server. Practicing by yourself is always a good way to start.
NOTE: make sure you put settings like this:
To surf in a straight line, strafe (a or d keys) into the side of the ramp (those things that float in the air), strafing right if you're on the left side, strafing left if you're on the right side. Think about this diagram: D/\A. Never press the back or forwards key while surfing because the forward key will make you slide off (more on the back key, s, later). Keep the mouse pointed in the direction you want to travel, the pitch of your cross hair doesn't matter, just don't look left or right if you want to go in a straight line.
To turn, when you are in the air strafe in the direction you want to turn, left or right, while smoothly changing your direction with the mouse in a centripetal fashion towards that direction. When your velocity is in the desired direction, stop strafing. As soon as you hit the new ramp strafe into the side of it again.
To pick up speed, start at the top of a ramp and move downwards. Make sure you do not move the mouse around too much when you are on a surf ramp then you will lose speed causing you to fall off when you get to the end or when you are surfing.
To ensure you don't lose speed when landing on a new surf, try to reduce the amount of force that your z-axis receives when landing. Do this by trying as best as possible to be looking and moving in the same direction as the surf when you hit it.
To get maximum distance when launching off a surf, try to be at the highest point you can get without losing speed. All surfs have different points which give the maximum distance when launch from, according to how they are carved.
To stop in mid-air, e.g. to land on a certain point, just press backwards (s), you will immediately stop and fall down . You will always fall exactly vertically (though you can strafe to reposition yourself while in the air), so if you look straight down you see the exact point of landing where your cross hair is. This is mostly needed above "teleportation-panels" or "landing-panels" (mostly with a water surface so you can land on it from high above).
To get faster you can start from the top of ramp then head down to bottom and up to middle again for best result...Just go up and down, like a wave.
When it is necessarily to gain lots of air very quickly, (Ex. To fly through the green loop on surf_10x_final) you must, at the VERY end of a ramp, move your mouse side to side fairly quickly while pointing in the direction (upward at some angle) that you want to fly. This can be very difficult to master but is very useful.
Landing (extra): When you leave a ramp and have to turn in mid air to land on the next ramp, a good way to gain good speed is to land near the top of the ramp holding away from the the ramp. Then hold onto to the ramp with the correct key. This doesn't make much sense, but go try and you'll get extra speed. Surfing is hard to describe, its best to just go learn. Just practice holding away from the ramp on bits where you enough speed to reduce friction and lost speed increase speed. I think a good map to go learn on is surf_legends as it has some nice ramps, make sure its a Death-match though. I'm a speed surfer and will race anyone who's up for a challenge.
Check out the BIG CS:Source Surf Faq