This document discusses various rules for using commas in sentences: 1) Use a comma before coordinating conjunctions (and, or, nor, but, yet, so) to join two independent clauses. 2) Use commas to separate items in a list of three or more items. 3) Use commas to set off introductory phrases or dependent clauses from the main clause. Commas should also be used to separate interrupting words or phrases from the main clause.