Check out "The Punctuation Guide"
    This easy-to-use site provides guidelines on every aspect of American punctuation.  (Note that British
    punctuation can be different.)  This online guide allows you to just click on a punctuation mark to find the
    rules and excellent examples on how to use it correctly!

1. Use apostrophes correctly
Maybe it’s because of its diminutive size, but the
apostrophe tends to be neglected and misused in
equal measure.

The apostrophe is used to form  possessives  (e.g.,
the school’s faculty, our family’s crest, the shirt’s
collar, Bill Thomas’s house) and certain  contractions  
(e.g., it’s, let’s, she’s, they’re, I’ve, don’t).

The apostrophe is not used to form most plurals (e.g.,
she is looking at several schools, the families have
similar crests, these shirts are on sale, we are dining
with the Thomases). There are three exceptions:
plurals of lowercase letters (e.g., dot your i’s and
cross your t’s); plurals of certain words used as words
(e.g., we need to tally the yes’s, no’s, and maybe’s);
and plurals of certain abbreviations (e.g., the staff
includes a dozen Ph.D.’s and four M.D.’s).
2. Know where to place quotation marks

Periods and commas go inside quotation marks, even
if they aren’t part of the material being quoted. All
other punctuation marks go outside the quotation
marks, unless they are part of the material being

“Any further delay,” she said, “would result in a lawsuit.”

His latest story is titled “The Beginning of the End”;
wouldn't a better title be “The End of the Beginning”?
3. Know how to punctuate with parentheses

When a parenthetical element is included at the end of
a larger sentence, the terminal punctuation for the
larger sentence goes outside the closing parenthesis.

When a parenthetical sentence exists on its own, the
terminal punctuation goes inside the closing

She nonchalantly told us she would be spending her
birthday in Venice (Italy, not California). (Unfortunately,
we weren’t invited.)
4. Use a hyphen for compound adjectives

When two or more words collectively serve as an
adjective before the word they are modifying, those
words should normally be hyphenated. The major
exception is when the first such word is an adverb
ending in -ly.

The hastily arranged meeting came on the heels of
less-than-stellar earnings.
5. Distinguish between the colon and the

The colon and the semicolon can both be used to
connect two independent clauses.

When the second clause expands on or explains the
first, use a colon. When the clauses are merely
related, but the second does not follow from the first,
use a semicolon.

Semicolon: Only a third of Americans have a passport;
the majority of Canadians have a passport.

Colon: Only a third of Americans have a passport: for
most, foreign travel is either undesirable or
6. Avoid multiple punctuation at the end of a sentence

Never end a sentence with a question mark or exclamation
point followed by a period. If a sentence ends with a period
that is part of an abbreviation, do not add a second period.  

I don’t particularly like the play Who’s Afraid of Virginia Woolf?
I didn’t like it even when I worked at Yahoo!  
I especially didn’t like it when I saw it at 5:00 a.m.
7. Use a colon to introduce a list only when the
introductory text is a complete sentence.

Not all lists should be introduced with a colon. The general
rule is that if the introductory text can stand as a
grammatically complete sentence, use a colon; otherwise,
do not.

Correct: Please bring the following items: a flashlight, a
comfortable pair of hiking boots, and a jacket.

Incorrect: Please bring: a flashlight, a comfortable pair of
hiking boots, and a jacket.

Correct: Please bring a flashlight, a comfortable pair of
hiking boots, and a jacket.

Correct: Please bring the typical evening hiking gear: a
flashlight, a comfortable pair of hiking boots, and a jacket.
8. Use commas to indicate non-essential information

If explanatory matter can be omitted without changing the
general meaning of the sentence, it should be set off with
commas. If the explanatory matter is essential to the
meaning of the sentence, do not set it off with commas.

Correct: The novelist Don DeLillo seldom gives interviews.

Incorrect: The novelist, Don DeLillo, seldom gives

Explanation: The identity of the specific novelist is
essential to the meaning of the sentence. Otherwise,
there is nothing to indicate which of the multitude of
novelists is being referred to.

Correct: America’s first president, George Washington,
served from 1789 to 1797.

Incorrect: America’s first president George Washington
served from 1789 to 1797.

Explanation: America has only one first president.
Identifying him by name is not essential to the meaning of
the sentence.
9. Use a dictionary

Is it U.S.A. or USA? Co-worker or coworker? Lets or let’s?
Teachers’ college or teachers college? Though these
examples implicate punctuation marks (the use or
omission of periods, hyphens, or apostrophes), the
correct form can be easily determined with a good
10. If in doubt, rewrite

The easiest way to solve a vexing punctuation problem is
to avoid it. If you aren’t sure how to properly punctuate a
sentence—or if the proper punctuation results in a
convoluted, confusing, or inelegant sentence—rewrite it.
Perhaps as more than one sentence.
Information taken from online source.