When you have a series of three or more words or phrases in a sentence, you need a comma before the last piece of the series (unless, of course, you're British; then you don't include a comma there).

"She would then take a newly finished quilt from her bag, wrap it around their quivering shoulders, tuck them in tight, and tiptoe away" (Jeff Brumbeau, The Quiltmaker's Gift).

"Avery put on clean underwear, clean blue jeans, and a clean shirt" (E. B. White, Charlotte's Web, 119).

The Tale of Despereaux being the story of a mouse, a princess, some soup, and a spool of thread (Kate DiCamillo)

"...Is it ridiculous for a very small, sickly, big-eared mouse to fall in love with a beautiful human princess named Pea?" (Kate DiCamillo, The Tale of Despereaux, 32).