The Associated Press has a stylebook with rules and standards used primarily in journalistic and news writing. The guidelines help writers present clear and concise information with consistent structure to keep readers focused. AP style dictates specific comma placement in a series and with dialogue, dates, numbers and titles like "Jr."
Specific AP Comma Rules
In AP style, omit the comma before the last item in a simple series, such as "Joe, John and Steve." If the series includes internal commas that necessitate semicolons or uses a conjunction such as "and," include the comma. For instance, AP would use the "serial" comma in this sentence: "The school offers courses titled Arts and Entertainment, Geology, History and Human Development, and Algebra." When writing dialogue, place commas inside end quotation marks: "Nobody was home," he said. Put commas between the day and year in specific dates, as in "Jan. 3, 2015." Leave out a comma between a person's name and the title "Jr." or "Sr.," as in "John Jones Jr." With the exception of street numbers and dates, use commas in numbers 1,000 and greater, as in "23,444 people."