In a Series
Use a comma to separate items in a series (three or more things).
You should even place a comma between the last two, although some writing style guidelines now omit this comma. In academic culture, we still use the serial or “Oxford” comma, so even punctuation rules have a rhetorical context. In some situations, you may not use the serial comma, but in academic writing you should, as illustrated in these examples:
She ran into the house, shut the door, and locked all of the locks because she thought a werewolf was behind her.