Punctuation

Probably the most important topic to at least partially grasp. I'll break it down piece by piece.

Periods
Ex: .
3 Rules:

1. Used to mark the end of a complete sentence.
2. Don't follow words or acronyms that end in periods with another period.
3. Questions which are indirect should be ended with a period.

Ellipsis Marks
Ex: ...
Ellipsis Marks are used when you omit a word, paragraph, phrase, line, or more from a quoted passage.
2 Rules:

1. Do not use more or less than three periods when forming an ellipsis mark.
2. When omitting long pieces use the ellipsis marks after the last punctuation mark.

Commas
Ex: ,
21 Rules:

1. Avoid confusion by separating words or word groups (3 or more items/objects/subjects) with a comma.
2. Separate adjectives with a comma where "and" can be inserted.
3. Separate -ly adjectives from other adjectives.
4. Before or surrounding the name/title of a person addressed.
5. Date
1. Outlaw the year from the day and the rest of the sentence after.
2. Leave the comma out when part of the date is omitted.
6. Outlaw the state from the city and the rest of the sentence after.
7. Set off titles and degrees with a comma.
8. Block out expressions which interrupt the sentence.
9. Mark the end of a weak clause with a comma, do not mark the end of a strong clause with a comma.
10. Put a comma at the end of phrases (3 or more words), otherwise it is optional.
11. If the object or subject is identified then the description following should be marked in commas. Likewise, if the object or subject is not identified then the description following should NOT be marked in comas.
12. Separate strong clauses with a comma, unless they are short. The comma is placed before the words: and, but, for, or, nor.
13. To avoid confusion, separate two sentences with a comma.
14. "A comma splice is an error caused by joining two strong clauses with only a comma instead of separating the clauses with a conjunction, a semicolon, or a period. A run-on sentence, which is incorrect, is created by joining two strong clauses without any punctuation." (http://www.grammarbook.com/punctuation/commas.asp)
15. If there is not a subject before the second verb in a sentence no comma is needed.
16. Introduce or Interrupt dialogue or quotations with commas.
17. Separate statements from questions.
18. Use a comma to separate the contrasting parts of the sentence.
19. When beginning the sentence with an introductory word (yes, well, now), isolate it with a comma.
20. "Therefore" and "however" are interrupters in the flow of the sentence, use commas to isolate them.
21. Block off introductory words (e.g., i.e., namely, for example, for instance, that is) when it is followed by a list of items.

Semicolons

Ex: ;

3 Rules:

1. Used in place of a period to conjoin two sentences where the conjunction has been left out. (I see this one get messed up so many times, conjunctions [and, or, but, because] are not allowed after a semicolon.)
2. Block off the sentence before introductory words (e.g., i.e., namely, for example, for instance, that is) when it is followed by a list of items. This is preferable over a comma.
3. Separate series with a semicolon when the series contains commas.

Colons

Ex: :

4 Rules

1. Use to introduce a list of items when introductory words are not used.
2. Following a salutation in a letter.
3. In context when a character is about to speak, but it starts in the next paragraph. (Needs to have a dialogue tag before the colon can be used.)
4. Introducing long quotations.

Question Marks

Ex: ?

3 Rules

1. When a question is asked.
2. When a statement is mixed with a question.
3. In gaming and texting language it can be used by itself to post the questions: What? Why? Who? Huh?

Exclamation Points

Ex: !

2 Rules

1. Used to show emphasis and surprise.
2. Refrain from using it too often in context, dialogue will show the emotion of the character better than a contextual exclamation point.

Quotation Marks

Ex: "

7 Rules

1. Periods and commas always go inside the marks.
2. If there is a quote used within a question the question mark goes outside the quotation marks.
3. If you are asking a question inside a quote the question mark goes inside the quotation marks.
4. Use apostrophes around quotes which are inside of quotes.
5. Quotation marks are only required when you are using a direct quote.
6. When writing a novel and a character/person/subject is speaking for more than a paragraph do not end the paragraph with a quotation mark. Instead start the next paragraph with one so the reader knows they are still hearing from the same character/person/subject.
7. When presenting a quote which may be confusing or with a spelling error put [sic] after the information/misspell to let the reader know it is the way the original piece was.

Parentheses

Ex: ( )

3 Rules

1. Enclose information which is used to clarify or is an aside.
2. Numbers or letters for listed items should be enclosed.
3. Periods only ever go inside parentheses if there is a complete sentence inside.

Apostrophes

Ex: '

8 Rules

1. Required in contractions.
2. Apostrophes are used to show possession. If they name/object/subject ends in an "s," however, then you do not put an 's you simply put an apostrophe.
3. Plural possession, both the noun and the object are pluralized, only the noun however will usually have the apostrophe.
4. Don't use an apostrophe for the plural of a last name.
5. If two or more people possess the same item together then only the last name mentioned should be marked with an 's. If they each own it separately, however, then you must mark each name with an 's.
6. Never use an apostrophe with possessive pronouns; i.e., theirs, yours, his, hers, ours, its
7. The word "it" only uses an 's when it is a contraction for "it is" or "it has."
8. Words should be possessive when they are in front of a -ing (gerund) word. Whether it be a noun or pronoun.

Hyphens or Dashes

Ex: -

Rules

1. Look up whether a word needs a hyphen.
2. Compound Verbs can be hyphenated or one word, check the dictionary.
3. If you can use the word "and" try a comma instead of a hyphen.
4. All compound numbers should be hyphenated.
5. Spelled out fractions should have a hyphen as well.
6. Words that begin with "self" should have a hyphen.
7. Can be used as a format in writing to have a continuation between thoughts or events.
8. Used in dates to say "from this time to this time."