Some rules of how to use hyphens correctly

Rule (1) When adverbs other than -ly adverbs are used as compound words in front of a noun, hyphenate. When the combination of words is used after the noun, do not hyphenate.

Examples:
He got a much-needed haircut yesterday.
His haircut was much needed.

Rule (2) Hyphenate all compound numbers from twenty-one through ninety-nine.

Rule (3) Hyphenate all spelled-out fractions, e.g., one-third, and one-half.

Rule (4) Use the hyphen with prefix re only when: the re means again AND omitting the hyphen would cause confusion with another word.

Examples:
Will she recover from her illness?
I have re-covered the sofa twice.
Re does mean again AND omitting the hyphen would have caused confusion with another word.