Use a hyphen to link modifiers before a noun. "Very" and adverbs that end in "-ly" are not hyphenated. 

    an English-speaking city
    a hard-boiled egg
    an awe-inspiring speech
    a very cute kid

Don't hyphenate compound modifiers after a noun.

Use hyphens when you write out numbers from 21-99.

    twenty-five
    ninety-eight

Use hyphens to keep words from being misread.

    a recreation area
    a re-creation of the event

Avoid hyphenating words or numbers that appear at the end of lines. Most word processors will automatically hyphenate for you (based on your alignment setting). Full justification (with aligned left and right margins) will have more hyphenated words than a left-justified selection.