There are only about a dozen rules on comma use, but a few are tricky. Let me try to clear things up:
When you list three or more items in a series, separate them with commas.
Standard English rules say to use a comma before the and. To make things confusing, journalism style books say you should never use a comma before the and. (Newspaper editors are stingy with punctuation.) Check to see which style your company prefers. If you are listing only two items in a series, don’t use the comma before and.
I will bring milk, creamer, and sugar to the conference room. (Standard English)
I will bring milk, creamer and sugar to the conference room. (Journalism)
I will bring creamer and sugar to the conference room.
When you are connecting two complete thoughts, put a comma before the and.
This rule also applies to the words but, or, nor, for, so, and yet, but and is the troublemaker because it’s prominent in the first rule above. Take this example:
Group A will attend training in the morning, and Group B will attend in the afternoon.
Each half of the example could stand alone as a complete sentence, so the two thoughts are separated by a comma and a connecting word (conjunction). But don’t forget the conjunction. It’s wrong to say, “Group A will attend training in the morning, Group B will attend in the afternoon.” That’s called a comma splice, and your high school English teacher frowns upon it.
Here’s where the real problem starts. Some business writers put commas with and because of the two rules just mentioned and then get in the habit of throwing in commas any time they see and. However, if a sentence simply contains two verbs and is not expressing two complete thoughts, no comma is needed:
Ted will present his draft of the annual report and then take questions.
The new computer system consolidates the two old servers and increases our networking capabilities.
Believe it or not, those two rules will take care of most of your comma problems. Other than that, where do the commas go?
Here: After an introductory word, phrase, or clause:
Before the boss arrived, my team checked the audio-video equipment for defects.
After the interviewees left the conference room, the management team voted for the top two candidates.
Not here: After a short transitional word or phrase.
Then I realized I was flirting with the boss’s wife.
In time we will expand the product line.
Here: Around the name of a person spoken to directly.
I think your problem, Stephen, is that you use too many commas.
Here: After a mild interjection.
Oh, I don’t know which laptop I like better.
Not here: After a strong interjection.
Damn! I spilled coffee on my keyboard!
Here: Around groups of words that you could remove from the sentence without changing its basic meaning.
My boss, an avid golfer, gets a new set of clubs every Christmas.
Bill Clinton, who was hounded by sex scandals, served two terms as president after serving as governor of Arkansas.
Not here: Around groups of words that are essential to the meaning of the sentence:
Employees who arrive late to work set a bad example for others.
The contracts that arrived on Monday were accidentally shredded.
Here: Around elements of dates and addresses.
The corporate office at 14 S. Market St., Pittsburgh, Pa., will be renovated beginning August 12, 2011, and won’t be finished for 10 years.
Not here: Between the month and year if no day is listed:
I started to work for Computers R Us in August 2010.
Here: Between adjectives (describing words) whose order can easily be changed:
It was a wordy, boring, useless report.
Not here: Between adjectives that need to be in a specific order.
He released the company’s 100-page annual report.
Here: To set up a quote.
According to the incident report, the employee said to the boss, “Shut the hell up!”
Not here: To set up a quote that flows with the sentence.
According to the incident report, the employee said that the boss should “shut the hell up!”
Check your documents to see if you can match each comma to a rule. If not, the comma is probably not needed. There is a technicality in most grammar books: use a comma any time the sentence would otherwise be misread or when the reader needs to be guided toward the correct interpretation, as in the classic expression below:
A woman without her man is nothing. (technically correct for one interpretation)
A woman, without her man, is nothing. (clarifying commas)
A woman: without her, man is nothing. (alternate reading)
Next time: Annoying Apostrophes