Righty Tighty, Lefty Loosey

From Bike Collectives Wiki

The standard threading on any kind of hardware follows the "lefty loosey, righty tighty" pneumonic devise for unscrewing or tightening bolts, screws, etc.

Holding a wrench at the 12:00 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."

So: To loosen, turn to the left (as defined above).

To tighten, turn to the right (as defined above).