Misplaced commas are the most common punctuation error I see. We all need help with commas at one time or another. Even experienced writers place them where they’re not needed and omit them where they are.
For example, in the sentence above, I originally typed a comma before that and, because I tend to pause there. I “hear” a pause, so I type a comma. Amy Einsohn, in The Copyeditor’s Handbook, calls writers like me “aural punctuators.” But commas exist not only to provide cues about when to pause, but cues about what grammatical elements of a sentence go together. Placing commas where they’re not grammatically useful creates a distraction. And as writers, the last thing we want is to distract the reader from our message.
As Einsohn puts it, “To master the syntactical approach to punctuation, you must be able to identify various grammatical units.” Yes, this means that to place your commas correctly you must be able to parse a sentence.
Back at the beginning of the year, I said this:
Rules for punctuation are almost inscrutable. The Chicago Manual of Style’s section on commas is 14 pages long. For a seminar handout, I condensed the bare minimum most writers need to know about commas, and it’s still almost a whole page. This kind of thing makes writers crazy and keeps copyeditors in business.
I excerpted that comma segment from the handout and put it into a PDF. I hope this comma cheat sheet is something you find useful.