1. Introductory Elements--Use a comma after introductory adverb clauses, participial phrases, long prepositional phrases, or elements that precede the main clause in a sentence.

Examples: Six days after the warranty expired, the car broke down.
Gazing across the channel, Matt listened to the tide come in.
Hidden in the gnarled brush, the thrush flung forth its soul in song.
Yes, you should try to memorize these six rules.
Fortunately, you have only five more to remember.

2. Interruptors--Use commas around elements that interrupt the sense of the main clause and do not add essential information (these are sometimes called nonrestrictive modifiers). NOTE: commas around interruptors come in pairs. If you use one comma, you must have a second one.

Examples: The team, exhausted after the grueling game, filed onto the bus.
The formula, which is on page 38, will solve all of your problems.
No one, not even the people on the front row, could see the film.

3. Afterthoughts--Use a comma before an element that comes after the main clause in a sentence and is nonrestrictive. The element may be helpful in expressing a certain idea; however, it is not an essential part of the sentence.

Examples: We foraged through the refrigerator, searching for artichokes.
The wind beat against the lonely child, who was huddled beneath the awning.
No one knew the correct answer, not even the professor.
The dealer drew our attention to the latest models, glistening beneath the spotlight.

4. Compound Sentences--Use a comma before the coordinating conjunction that separates the two independent clauses in a compound sentence. (Do not make the mistake of throwing in a comma before every coordinating conjunction. Make sure that the conjunction is joining two complete sentences.

Examples: It is bad enough that the sidewalks are in such horrible condition, but it is even worse that the streets are full of potholes.
A driver has to avoid broken beer bottles, or he is likely to have a flat tire.
Dangerous chemical substances are polluting our water supplies, and debris is piling up outside our doors.

5. Items in a Series--Use commas between each item in a series of three or more (don't forget the comma before the conjunction joining the last two items in the series).

Examples: Coke, Pepsi, and R.C. manufacture carbonated beverages.
The vandals had torn the screens from the window, shattered the glass, and entered the cabin.
Diedrich,Geoffrey, Humphrey, and Washington were the pseudonyms that he used.

6. Equal Modifiers--Use a comma between two modifiers of the same type that are modifying the same word. One test to see whether you have equal modifiers is to insert the word and between the modifiers. If this insertion can be made without altering the meaning of the sentence, the modifiers are considered equal. They should be separated with a comma.

Examples: The dull, mildewed walls were covered with antique carvings.
Let me never feel the fateful thrilling that devastates the lovelorn, dejected wooer's frame.
A white-shouldered, broad-browed maiden opened the gate.
Jay could not see that Daisy was a self-centered, egotistical socialite.