The hyphen is a punctuation mark that follows specific guidelines for correct spelling of compound words and words that work together as an adjective. The hyphen is used when writing forms of fractions and compound numbers. You should hyphenate words with the prefixes all-, ex-, and self- and with the suffix -elect. A hyphen is also used to divide words at the end of the line of typing or hand-written pieces.
Source: Kathleen Hanley
The video gives clear instructions on how and when to use hyphens.
Source: http://youtu.be/R0uBCEII254
