How do you adjust an acoustic guitar truss rod?

The answer is "it depends". There are a few variables: is the action too high, too low, where is it off (saddle, nut, 12th fret). I'll give a brief explanation.

THIS ADVICE HAS NO GUARANTEE - IF YOU ARE UNSURE, TAKE IT TO A LUTHIER

1) too high

-NUT: you can either file the nut with nut files (expensive) or sand some of the bottom of the nut off.

-NECK: adjust your truss rod

-SADDLE: sand a small amount of material from the bottom of the saddle

2) too low

-NUT: buy a new nut, or add krazy-glue and baking soda to fill in the grooves, refile to your liking

-NECK: adjust truss rod

-SADDLE: buy a new saddle or shim the saddle you have