Teams have randomly assigned roles.
F1 to toggle help.
WASD to move.
Press C to open and close the map.
Press E to enter the seat closest to you in a car/helicopter, and hold E to exit.
Press Tilde (the squiggly thing next to 1) to drop the item you have equipped, and Shift+Tilde to drop items in your left hand.
Press a number key (shift + number for left hand) to place the item you're holding in your inventory, press again to equip that item.
Hold Space while driving for E-brake.
Press Space when you're dead to switch the player you're observing in Round Mode.
Open UDP port 27584 if you want to host a server.
Press F to switch items between left and right hands.
Press F5 on the server to restart the game.
How the voice chat works:
In the voice options menu you can configure to broadcast voice when over a minimum level or use push to talk (hold a key while talking to broadcast, default V).
Cell phones: click on this link for an explanation.