You use the period, by far the most common of the end punctuation marks, to terminate a sentence that makes a statement. You may also use periods with imperative sentences that have no sense of urgency or excitement attached:

Without a doubt, Lady Emily was much happier after her divorce.

Turn right at the stop sign.

Bring me a cup of coffee and a cheese danish.

When you want to express a sense of urgency or very strong emotion, you may end your imperative sentences and statements with an exclamation mark:

Look out below!

Leave this house at once!

I hate him!

Exclamation marks are, however, rare in formal writing. Use them sparingly, if at all.

You should use the question mark at the end of a direct question:

Who's on first?

Where is my flowered cape?

Be careful not to use a question mark at the end of an indirect question. Indirect questions are simply statements, and therefore end with a period:

I wonder who was chosen as Harvest King in the county fair.

She asked if she could play pinball.

The teacher asked who was chewing gum.

The exact rules for quotation marks vary greatly from language to language and even from country to country within the English-speaking world. In North American usage, you should place double quotation marks (") before and after directly quoted material and words of dialogue:

One critic ended his glowing review with this superlative: "It is simply the best film ever made about potato farming." May replied, "This is the last cookie."

One critic ended his glowing review with this superlative: "It is simply the best film ever made about potato farming."

May replied, "This is the last cookie."

You should use an apostrophe to form the possessive case of a noun or to show that you have left out letters in a contraction. Note that you should not generally use contractions in formal, academic writing.

The convertible's engine has finally died. (The noun "convertible's" is in the possessive case)

I haven't seen my roommate for two weeks. (The verb "haven't" is a contraction of "have not")

To form the possessive of a plural noun ending in "s," simply place an apostrophe after the "s."

As noted in the section on commas, you can use a dash at the beginning and end of parenthetical information. Usually, you will use dashes when you want to emphasise the information, but you might also use them if the parenthetical information is too long or abrupt to be set off with comma

I think you would look fine wearing either the silk blouse -- the one with the blue pattern -- or the angora sweater. (abrupt interruption)

The idea of returning to the basics in the classroom -- a notion which, incidentally, has been quietly supported for years by many respected teachers -- is finally gaining some currency with school administrators. (lengthy interruption containing internal commas) s