Walking was possible in 1.3, it's not anymore. If you wanna walk without being heard you have to duck (or crawl but that takes time).
You Speed run for short periods with the Shift Key.
My Mapping:
Mouse 1: Fire
Mouse 2: Secondary Fire (sniper rifle scope and MG barbete)
Middle Mouse button: Need to set it up
Foward: W
Backward: S
Strafe left/right: A and D
Duck: Q (should remap this to middle mouse)
Jump: Space (never use the thumb for anything else)
Panick Run: Shift (use shift + W)
Change weapons: Normal thing, push 1 for knife then click mouse and it changes.
Note, that grenades have a 5 second timer, when you see a grenade is thrown at you, if you have time, you can pick it up. Go to it, look at it, push E (use key) and then throw it away FAST.
You can time your own grenades like this, drop it on the gorund, pick it up, wait a seonc or two and throw it.