Use a comma before and , but , for , nor , or , so , or yet when it joins independent clauses in a compound sentence.

Do not confuse a compound ssentence with a siimple sentence containing a compound verb. Usually, no comma is needed between the parts of a compound verb. COMPOUND SENTENCE: We ran relay races first, and then we ate lunch. SIMPLE SENTENCE CONTAINING A COMPOUND VERB: We ran the relay races first and then ate lunch. However a compound verb made up of 3 or more verbs generally does require commas. EX: We ran the relay races, atelunch, and the prepared for the individual races.