Using commas effectively

Using commas effectively 
 Here we'll consider four main guidelines for using commas effectively. But keep 
in mind that these are only guidelines: there are no unbreakable rules for using 
commas--or any other marks of punctuation. 
1. Use a Comma Before a Coordinator 
Use a comma before a coordinator (and, but, yet, or, nor, for, so) that links two 
main clauses: 
 "The optimist thinks that this is the best of all possible worlds, and the 
pessimist knows it." (Robert Oppenheimer) 
 "You may be disappointed if you fail, but you are doomed if you don't 
try." (Beverly Sills) 
However, do not use a comma before a coordinator that links two words or 
phrases: 
 "Jack and Diane sang and danced all night." 
2. Use a Comma to Separate Items in a Series 
Use a comma between words, phrases, or clauses that appear in a series of three or 
more: 
 "You get injected, inspected, detected, infected, neglected, and 
selected." (Arlo Guthrie) 
 "It is by the goodness of God that in our country we have three unspeakably 
precious things: freedom of speech, freedom of conscience, and the 
prudence never to practice either of them." (Mark Twain) 
Notice that in each example a comma appears before but not after the coordinator. 
3. Use a Comma After an Introductory Word Group 
Use a comma after a phrase or clause that precedes the subject of the sentence: 
 "When you get to the end of your rope, tie a knot and hang on." (Franklin 
Roosevelt) 
 "If at first you don't succeed, failure may be your style." (Quentin Crisp) 
However, if there's no danger of confusing readers, you may omit the comma after 
a short introductory phrase: 
 "At first I thought the challenge was staying awake, so I guzzled venti 
cappuccinos and 20-ounce Mountain Dews." 
4. Use a Pair of Commas to Set Off Interruptions 
Use a pair of commas to set off words, phrases, or clauses that interrupt a sentence: 
 "Words are, of course, the most powerful drug used by mankind." (Rudyard 
Kipling) 
 "Literature is all, or mostly, about sex." (Anthony Burgess) 
But don't use commas to set off words that directly affect the essential meaning of 
the sentence: 
 "Your manuscript is both good and original. But the part that is good is not 
original, and the part that is original is not good." (Samuel Johnson)