1. Separate phrases that don't need to be there.
Ex: My goldfish, Bubbles, is a really fast swimmer.
2. When linking two independent claues with a conjunction.
Ex: I want to hangout with my friends, but i have to go to my football tournament.
3.When you're addressing some one in particular .
Ex: Let's go eat, Donald.
4.When making a list.
Ex: Peanut butter, jelly, and bread.
5.When you have more then one adjectives modifying a noun.
Ex: The cute, cuddly pug.
6. After introduceing phrases or clauses.
Ex: Once you finsh your homework, you must clean the dishes.
The "other" three
Ex: Decmber 31, 2012
8. End of a letter
Ex: Love, pie
Ex: Cumming, Georgia
When not to use a comma
1.When separating two independent clauses without a conjunction .
2. After a conjunction .
3. When seperating a dependent and independent clause wtih a conjuction.