The basic setup for Nexuiz is:
Forward: W
Backward: S
Left: A
Right: D
Fire: Left-click Control
Alt fire: Right-click Alternate
Crouch: Shift
Jump: Space
Laser: 1
Shotgun: 2
Machine gun: 3
GrenadeLauncher: 4
Electro: 5
Crylink: 6
NexGun: 7
Hagar: 8
RocketLauncher: 9
This entire setup is fully customizeable by the user, either through the options menu (click options>controls) or through the console (press "~" to access console, then type "bind <key> <action>" to set a key to an action.)
Example of console key binding change:
bind q quit
The console command above would bind the "q" key to quit the game.