Not bad...
Controls are like any other FPS; use either w, s, a, d, to move or use the arrow keys...
One lesson you'll learn really fast when playing CS:S... DON'T DO ANYTHING STUPID!! If an opponent is behind a corner, don't rush in acting like Rambo; try to take him out by shooting AROUND the corner, then move on after he's dead.
Grenades can help, or hinder your team's progress in a map, especially FLASHBANGS. Throw them AWAY from you and your team members, or risk being temporarilly blinded and ultimately screwed because you weren't paying attention to where your enemy was and they managed to gun you down while you were waiting to be able to see again! The same goes for your guns: USE WHAT YOU'RE FAMILIAR WITH; if you use an SMG against an auto-shot, there's a good chance you're gonna die. Use the opposite of your enemy's weapon.