Who knew there was so much to learn about punctuation marks? To make it as easy as possible, review the following fifteen rules from time to time and you'll be a punctuation pro:
1. A period shows where sentences end, separates the initials of some acronyms, and ends many abbreviations.
2. Don't double-space after a period at the end of a sentence; the word processing program will adjust the space for you.
3. Commas, signaling natural pauses and adding clarity to what you're writing, should be used before conjunctions and before the final or or and in a series.
4. Semicolons (weak periods) separate two thoughts of equal rank; these are thoughts that could be turned into independent sentences.
5. Colons are used to do the following: introduce lists, separate thoughts (when one further explains the other), distinguish hour and minutes, cite chapter and verse, separate title and subtitle, and end formal salutations.
6. Ellipses indicate that words or sentences have been omitted, or a thought has trailed off . . .
7. Apostrophes show possession, not plurals (except for its [possession] and it's [it is]), as well as indicating missing letters when a verb has been contracted.
8. Quotation marks indicate that someone is speaking or that material has been taken from another source.
9. In American English, commas and periods are usually inside the quotation marks; colons and semicolons are outside; and dashes, question marks, and exclamation points are inside or outside depending on usage.
10. Exclamation points follow interjections, and you should use them sparingly. Please!
11. Question marks show that an answer is requested or that the writer is unsure of a specific fact.
12. Hyphens connect words with prefixes, suffixes, or other words.
13. Dashes, which are about the length of the letter m, signify a dramatic break in thought, while shorter dashes, known as en dashes, which are the length of the letter n, are used between a range of dates, times, or numbers.
14. Parentheses enclose figures in a numbered list within a sentence or set off explanatory material (facts that add substance).
15. Brackets indicate editorial comments, corrections, or clarifications – or further set off text within a parenthetical phrase.
Source: The Gremlins of Grammar