1. Use a comma to separate items in a list (but beware of the serial comma).
The English language uses a comma to separate three or more items in a series. Look at the following example.
That girl is obsessed with commas, semicolons, and em dashes.
Easy, right? But hold it! Before you go throwing in commas all willy-nilly, you first have to decide what flavor of English you’re using. No, cookie dough is not a valid answer (but it is probably a good answer). Take a look at the example again.
See that comma before “and,” the conjunction? That’s called a serial comma, which separates the last two items in a list. You have to decide on a flavor of English (that isn’t cookie dough), because each flavor has a different ruling on the use of the serial comma.