In a series:
Separate all items in a series of three or more with commas: His influences included Charlie Parker, the Ramones, and Gertrude Stein. This is an exception to AP style, which omits the final comma, also known as a serial or Oxford comma. When writing specifically for the news media, omit the final comma: She studied math, chemistry and physics.
Use a comma before and after a state abbreviation: Long-distance information, give me Memphis, Tenn., and help me find a party that tried to get in touch with me.
Use commas in numbers of four digits or more (the school received 1,244 applications), except when referring to temperatures (2200 degrees Fahrenheit) or page numbers (page 1446). Also see Dates and Times.
After names and appositives:
Commas are not needed between nouns identifying the same person: He dropped his son Jim at the school. However, when an appositive provides more detail (which son? what age?), commas are used: He dropped his son, Jim, at the school while his other son Jason slept. He dropped his son Jim, a sophomore, at the school.