1. Hyphens
The hyphen’s main purpose is to glue words together. They notify the reader that two or more elements in a sentence are linked. Although there are rules and customs governing hyphens, there are also situations when writers must decide whether to add them for clarity.

2. Rule 1
Generally, hyphenate two or more words when they come before a noun they modify and act as a single idea.
This is called a compound Adjective.
Example:
State-of-the-art technology.
We live in an off-campus apartment.

3. Rule 2
A hyphen is frequently required when forming original compound verbs for vivid writing, humor, or special situations.
Example:
The man video-gamed his way through life.
Mr. Swain English-taught most days.

4. Rule 3 Hyphens are often used to tell the ages of people and things.
A handy rule, whether writing about years, months, or any other period of time, is to use hyphens unless the period of time is written in plural form.
Example:
I have a two-year-old nephew.
My nephew is two years old.

5. Rule 4 Use a hyphen to solve a possible problem. Example: Confusing:
I have a few more important things to do.
Clear:
I have a few more-important things to do.
Without the hyphen, it’s impossible to tell whether the sentence is about a few things that are more important, or a few more things that are all equally important.

6. Rule 5
When using numbers, hyphenate spans of time, distance, or other quantities.
Example:
3:15-3:45 p.m.
people

7. Rule 6
Hyphenate all compound numbers when you write them out from twenty-one through ninety-nine.
Example:
Seventy-eight kittens
Twenty-nine cents an hour.

8. Rule 7 Hyphenate all spelled-out fractions. Example:
No more than seventeen-thirty-eights.
She’s only five-sixths crazy.

9. Rule 8 Hyphenate most double last names. Example:
Lady Sansa Stark-Bolton won’t make it past season six.

10. Rule 9
Hyphenate prefixes when they come before proper nouns or proper adjectives.
Example:
The party is going to be mid-July.
One Direction is going on a trans-American tour.

11. Rule 10
Hyphenate prefixes that end with a vowel that hyphenated word begins with.
Example:
Ultra-ambitious
Semi-invalid
Re-elect

12. Rule 11
Hyphenate all words that begin with the prefix Self, Ex, and All.
Example:
Self-esteem
Ex-associate
All-knowing

13. Rule 12
Suffixes are not usually hyphenate with some exceptions: Style, elect, free, and based.
Example:
Modernist-style paintings
President-elect…
Sugar-free candy
Oil-based lotions