Righty Tighty, Lefty Loosey
The standard threading on any kind of hardware follows the righty tighty, lefty loosey mnemonic device for unscrewing or tightening bolts, screws, etc.
Which way is left and which way is right?
Holding a wrench at the 12 o'clock position determines whether you are turning left or right. If the wrench (in the most upright, 12:00 position) falls to the left, you are going "lefty loosey." If the wrench falls to the right, you are going "righty tighty."
Directions
To loosen, turn to the left (as defined above).
To tighten, turn to the right (as defined above).