Commas are the most used and most frequently misused punctuation marks. Basically, the comma is used to signal a pause. It can help make the meaning of a sentence more clear, but if it is used carelessly, it can cloud the meaning of a sentence entirely. The most important rule of thumb to follow when using commas is: use a comma only when you are sure you need it.
1) Use commas to separate three or more items in a series.
Ex: She enjoys drawing, reading, and playing basketball.
2) Use a comma between two independent clauses if they are connected by such words as: and, but, for, nor, or, yet, so.
Ex: I wanted to go, but I didn't have enough money.
3a) Use a comma after a long introductory phrase or clause.
Ex: When the time comes, everyone will know the truth.
3b) Use a comma after a short introductory phrase or clause if it is necessary to avoid unclear meaning.
Ex: While eating, the group discussed plans for the afternoon. (Without a comma, it may look as though someone or something were eating the group.)
* The words yes and no are generally followed by a comma when they begin a sentence. So are words such as the following:
however, in fact, of course, incidentally, well, by the way.
4) Use commas on both sides of a word, or group of words, that interrupts the flow of the sentence.
Ex: The Simpsons, for example, has been accused of promoting stereotypes.
* Some expressions that are generally set off with commas include: however, of course, therefore, in fact, to tell the truth, by the way, at any rate, I think, finally.
5) Use commas to set off nonessential material.
Ex: Fox Mulder, who has a terrible habit of losing his gun, ran after the suspect.
6) Use a comma after every item in an address or date.
Ex: Sunday, October 13, 1961
* 2630 Hegal Place, Alexandria VA,