Rules are Made to be Left Up to Style

It drives me nuts that we have unbreakable rules for such small things like:

• west as a direction, but West as a location
• If you want to shorten a word it's 'em and not 'em (of course no curly quotes here)
• How to properly use ellipsis 
• Three different types of dashes 

But when it comes to the bigger things like capitalization and when you want to use commas, errors in writing become "the author's style." 

What I’ve learned so far in my editing class:

• Selling 100,000 books in a year makes you a New York Times Best Selling Author
• If you want to work with the Big Publishing Houses you need a Literary Agent
• Do Not become attached to the title you come up with
• Always get veto rights on you cover art
• Cover Art can make or break a book
• Always avoid Vanity Presses
• Keep a reference list on hand of all the words you have trouble spelling
• Keep a story specific list of words or phrases to save time on double checking

How to Write Numbers:

The most important thing is that you keep what you do consistent.

  Also use your best judgement when writing numbers in dialogue. 

Years

• Spell out centuries
• twenty-first century
• Use apostrophes to show missing numbers
• always angled to the left ′70
• Use numerals for dates
• September 17, 2012
• Don’t use apostrophes for plural years
• 1920s

Spell Out

• If followed by hundred, thousand, hundred thousand
• Any number that comes at the beginning of a sentence
• work it so years don’t end up here
• Always write out centuries
• Measurements
• unless it’s normally seen as a numeral, 50 gallons
• Simple Fractions
• unless mixed with whole numbers
• Monetary Values
• unless it’s complicated or a lot of values in one paragraph
• Times followed by o’clock and half-hour or quarter times
• unless it’s specific: 4:18
• don’t use numerals for midnight or noon
• Spell out numbered streets up to 100

Use Numerals

If followed by million, billion, etc

If a complicated number

• 54,321 instead of spelled out

If there are a lot of numbers in one paragraph

Abbreviated unit of measurement

• 50 mph
• no numeral then spell out the measurement

Percentages

• if using % no space between numerals and symbol

For pages, chapters, volumes, verse numbers, illustrations, and tables