commas

It's not the end of the world, but as a matter of good form you should not use a serial comma before a conjunction.
'planes, trains and automobiles' not 'planes, trains, and automobiles'
In the cases of simple conjunctions using 'and,' 'but,' 'or,' etc. only use a comma if the phrase following the conjunction is a complete sentence.

Correct: Bert and Ernie left their apartment to go shopping for massage oils and to return Big Bird's copy of Grand Theft Auto 7: Sesame Street Killzone.

Correct: Bert and Ernie left their apartment to go shopping for massage oils, and after lunch they returned Big Bird's copy of Grand Theft Auto 7: Sesame Street Killzone.