Multi-word describers

When you use several words to modify a noun, those words must be hyphenated. For example, all of these words--"I," "don't," and "care"--are used as an adjective phrase to describe attitude in this sentence: "He has an I-don't-care attitude."
Consequently, those three words have to be hyphenated.

Question Marks to Indicate a Question Within a Sentence

When a short direct question falls within a sentence, the question is set off by commas and a question mark is used at the end of the sentence.

Example:
We´re going out to dinner, aren´t we, after the movie?

Possessives

Contrary to what many of us were taught in school, if a singular noun ends in an "s," it still gets an extra "s" added after the apostrophe if you pronounce the extra "s."

Examples:
our boss´s office
St. Louis´s Gateway Arch

If it is difficult to pronounce the extra "s," then you only add an apostrophe.

Examples:
New Orleans´ Bourbon Street
Los Angeles´ smog

Parentheses

If a parenthetical phrase falls within a sentence, the ending period, or other punctuation, should be placed outside the ending parenthesis; however, if the parenthetical phrase follows a complete sentence (after a period), the period for the parenthetical phrase goes inside the ending parenthesis.

Ex: Your account value is determined by multiplying the number of shares by that day´s closing price (net asset value).
Ex: Your account value is determined by multiplying the number of shares by that day´s closing price. (The closing price is referred to as the net asset value.)

Punctuation With Quotation Marks

Periods and commas always go INSIDE the closing quotation mark.
Semicolons and colons always go OUTSIDE the closing quotation mark.
Question marks and exclamation points vary, depending on whether they apply only to the quoted material or to the entire sentence.

Miscellaneous Possessives

driver´s license
traveler´s check
collector´s item
cashier´s check
visitor´s permit
seller´s market (or buyer´s market)
finder´s fee
dog´s life
rabbit´s foot
bull´s-eye
monkey´s uncle
proofreaders´ mark
lovers´ lane
workers´ compensation
witches´ brew
women´s room
states´ right
state´s evidence
citizen´s arrest
citizens band
teacher´s pet
teachers college

Commas With Abbreviations

The abbreviations for "etc.," "i.e.," and "e.g." and the abbreviations for academic degrees are parenthetic and should be punctuated accordingly.

Examples:
Letters, packages, etc., should go here.
John Wilson, Ph.D., presided.

Lowercase Abbreviations

a.m.
p.m.
i.e.
e.g.
f.o.b.
e.o.m.

BUT:
rpm
ips
mpg
mph

Compound Possessives

To determine how to punctuate a compound possessive, first determine ownership.

If two people own something jointly:
Ben and Jerry´s Ice Cream

If two people both own separate things:
Ben´s and Jerry´s houses (We´re assuming that they each have a house that they do not own jointly.)

All-Caps Abbreviations

These normally do not require abbreviations:

IBM
MIT
AMA
UAW
AICPA
NCAA
NAACP
NFL
IRA
IRS
UN
TLC
PSAT

Abbreviations: Academic Degrees & Religious Orders

Abbreviations of academic degrees (and religious orders) require a period after each element in the abbreviation but no internal space.

B.S.
M.B.A.
Ph.D.
LL.B.
Litt.D.
Ed.D.
B.Ch.E.
B.Arch.
M.Div.
M.D.
D.D.S.
R.N.
S.J.
O.S.B.
S.N.D.

Hyphens and Compound Nouns

Note the following differences:

I am writing as a follow-up to ...
I am going to follow up on ...

1999 tax year
tax-year 1999

The explanation? A compound noun becomes hyphenated when used as an adjective.

Hyphens

Words gradually evolve from two words to hyphenated to one word. For example: bell boy, bell-boy, bellboy. Use a dictionary to determine the correct form. If it is not listed in the dictionary, assume two words.

Spacing After Periods

We were taught in typing class to space twice after a period at the end of the sentence. That´s correct for a typewriter. However, most of us use computers with proportional characters. In that case, you only space once after the period.

To see examples of monospacing (which gets two spaces after a period) and proportional characters (one space), compare two common fonts.
Courier is monospacing.
Times Roman is proportional.

Introductory Clauses

A colon is used after an introductory clause that contains a complete thought and will be followed by a list.

To reregister the account, we must receive the following documentation: a copy of your divorce decree, a completed application, and written instructions from you.

Plural Possessives

children´s accounts (NEVER childrens´ accounts)
men´s neckties (NEVER mens´ neckties)
women´s dresses (NEVER womens´ dresses)