What is the proper usage of the hyphen?

Answer 1

Hyphens are typcally used to join phrases that behave as a single adjective:
four-wheel-drive truck
three-year-old child
ten-story building
six-foot-long log
four-way intersection

It is also used with two-word numbers:
twenty-one
fifty-five
etc.

Does that do it? There may be more, but that's all that come to mind.

Answer 2

http://en.wikipedia.org/wiki/Hyphen

A hyphen ( -, or ‐ ) is a punctuation mark. It is used both to join words and to separate syllables. It is often confused with a dash ( –, —, ― ), which is longer. Hyphenation is the use of hyphens.