Rule 1 - Use commas in compound sentences when clauses are separated by a conjunction such as "and," "but," "for," etc. ex: She managed the restaurant, but he did the cooking
She didn't like the Orioles, nor did she like the Redskins.
Rule 2 - Use commas to separate elements in a series.
ex: I like the colors red, orange, yellow, and green.
The tall, dark, handsome man came over and said hello.
Rule 3 - Use commas when attributing from quoted material.
ex: He said, "It's a beautiful day outside."
She said, "I completely agree with you."
Rule 4 - Commas follow introductory matter, such as after an introductory adverbial clause.
ex: When the team was forced to kick, the coach sent in his best players.
After they won, the coach bought the team ice cream.
Rule 5 - Commas follow the salutation of a friendly letter and the complimentary close of any letter. They also follow capitalized elements, like the complimentary close.
ex: Dear James,
Sincerely, Jill
Rule 6 - Commas follow all items in a date or full address:
ex: January 1, 2009 was New Year's Day.
I lived in Baldwin, NY until I was 10.
Rule 7 - Commas surround nonessential words or phrases:
ex: Well, we will just have to walk home.
Unfortuantely, it rained on my birthday.
Rule 8 - Commas surround words or direct address
ex: Maria, please pass the butter.
I can see, Fred, that you're lazy.
Rule 9 - Commas indicate omitted verbs, usually expressed in another part of the sentence
ex: Talent often is inherited; genius, never.
Men are from Mars; women, from Venus.