Another section of "The Second Mouse Gets the Cheese" deals with matters of editing. Here's a bit of what I have to say about commas:
RULE: A NATURAL PAUSE INDICATES A COMMA.
Listen for the pauses. Add commas.
As an aside, academics sometimes argue over what is called the Oxford comma. That’s the one that appears before the ﬁnal “and” in a series. When I read a series of terms (like pens, notebooks, pencils, and erasers), I hear a pause after pencils, so I always use the Oxford comma. In other words, I follow my own rule about hearing commas. You may, however, encounter an editor who thinks that extra comma is not only unnecessary but adds an extra expense--one likely to drag the publisher into instant bankruptcy. She will tell you that a comma takes the place of an “and”, so you never need both. My advice? Don’t waste your breath on an argument in which both sides are right. Gracefully bow out, taking your Oxford commas with you. (Because editors always win.)