Hyphens

Use a hyphen in certain compound words (brother-in-law, self-confident) or in a compound adjective (That is an over-priced sweater.)

Use a hyphen in compound numbers from twenty-one through ninety-nine

Use a hyphen in spelled-out fractions (one-half, three-fourths)

To see if you need a hyphen or not between two words, try this:

Read the words separately with the word they're describing. If they don't make sense separately, you need a hyphen between them. If they do make sense separately, you don't need a hyphen between them.

For example, self motivated student. Try each describing word separately. Ask yourself: Is it a self student? Is it a motivated student? Well, the motivated part makes sense, but not the self student part. Therefore, you need to make it one word, self-motivated. Now, self-motivated student makes sense.