Often-Overlooked Rules of Grammar

It's the little things that can make all the difference. The things you might not notice when they're right, but you always notice when they aren't. Those things that, once you have learned the right way, will make you cringe when seen any other way.

Hyphen vs. dash.
There are actually three hyphen-like characters: The hyphen itself, the en dash and the em dash, with specific rules when you should use each one:

Hyphen

• Used as an automatically-generated dash when a multi-syllable word breaks at the end of a line
• Use the hyphen to link compound modifiers and other hyphenated words (Catherine Zeta-Jones)
• Use it for telephone numbers (e.g. 800-555-1212)
• Do not put a space before or after a hyphen

En Dash

• Use as a substitute for "through" (1990–2000)
• Do not use with "from" (I attended college 1996–2000, not from 1996–2000)
• No space before or after an en dash

Em Dash

• Use it to signify an abrupt change of meaning or thought in a sentence (The em dash—a long dash used to separate a thought in a sentence—is twice as long as an en dash.)
• Do not put a space before or after an em dash

Avoid underlines
The underline is a visual relic of the typewriter age. The typeset equivalent is Italic.

Its vs. It's
It's a dog eating its dog food.

It's is a contraction, a combination of the pronoun it and either the verb is or has. Examples of contractions: He'd and they're. Use its, without the apostrophe, to refer to a possessive, like hers or his. Though most possessives (Jimmy's, for example) use an apostrophe, its does not.

Ellipsis…
Use an ellipsis to replace omitted text. These dot-dot-dots are subject to their own grammar rules that are often overlooked. If words are omitted at the end of a sentence, use an ellipsis followed by a period. If sentences are omitted between other sentences within a quotation, use an ellipsis after the period.

Quotes vs. inch marks
Typewriters didn't differentiate between quotes and the inch symbol, but fonts do. Unfortunately, keyboards do not have a smart quote key. You have to know how to access the right character. To make it easier, a number of word processing and layout programs support smart quotes. With smart quotes, straight quotes convert automatically to open-close quote pairs—if you manually type text.

[Brackets] vs. (parentheses)
Brackets are used to enclose explanatory material inserted into a quotation by someone other than the original writer or person being quoted [I did not know that! –Editor].

Use parentheses (the marks surrounding this) as a way to provide an additional or alternative explanation of the subject at hand: The record low for July 9 was 60° (15°C).

Acronyms are good examples of when to use parentheses: Parent Teacher Association (PTA).

Spell out numbers under 11
The rule for numbers: Spell out when they are less than 11 and use numerals for 11 and above. Always spell out numbers when they begin a sentence (Four score and seven years ago), except for calendar years (1776). Use numerals for percents (5%), time (8 minutes; 3:00 pm) and ages (the baby will be 6 months old tomorrow).

Colons and semi-colons
Use semi-colons to connect two closely related sentences and avoid run-ons. Do not capitalize the word following a semi-colon. Rely on a colon when announcing a list or as a way to transition to a similar point of focus. Unlike the semi-colon, capitalize the initial letter of a word immediately following a colon: Use colons and semi-colons just like this; don't worry, this is the right way!

Avoid double spacing
Never use double spacing to separate sentences. It is an outdated holdover from the days of the typewriter. Double spaces create gaps in paragraph spacing and make the eye jump around the page. Layout and word processing software require only one space. Use just one space after periods, colons, exclamation points, question and quotation marks, etc. With the space bar, less is definitely more.