This link provides sections on all kinds of punctuation uses. Check it out!

http://www.libraryonline.com/default.asp?pID=29

ALSO, a hilarious book on this topic is "Eats Shoots and Leaves" by Lynn Truss. She is a professional writer, and her views on commas AND apostrophes are classic. There are neat bits of trivia also. For example: Do you know where the question mark came from?

Your local library or bookstore should have it.