When it comes to punctuation, knowing when, and when not to, use commas in writing is the biggest problem most writers face. Correct comma usage can be hard to learn, but once it is learned, writing becomes both easier and better.
Many writers have been told to use a comma anytime they would pause while reading a piece of writing. While following this suggestion will lead to correct comma usage in some situations, there are many other times when following this guideline will lead to unnecessary comma usage. Instead of using this as a guideline, there are several rules that dictate when commas should be used. Learning and practicing these rules will help any writer become better at using commas.
Rule #1: Use a comma to separate independent clauses linked with coordinating conjunctions.
If you have what can be two separate sentences but want to make them one (creating a compound sentence), use a comma and a coordinating conjunction (for, and, nor, but, or, yet, so) to link them.
EXAMPLE: My English Instructor was a good teacher, and he taught me a lot about the
Rule #2: Use a comma at the end of an introductory element.
This rule can be confusing because introductory elements are often hard to identify. Essentially, an introductory element begins a sentence by providing a transition from the last sentence or background information before the independent clause.
EXAMPLE : Prepositional phrase: In a hard fought contest, the home team prevailed after two overtimes.
Rule #3: Use a comma to set off nonessential elements.
A nonessential element is a word, phrase, or clause that is not needed to complete a sentence. In other words, it can be removed and the sentence still makes sense and is grammatically correct. If removing the element changes the meaning of the sentence, it is essential. Nonessential elements need to be offset with commas, both before and after.
EXAMPLE :
I went to the movies with my neighbors, Ron and Sally, and then we went to dinner.
When using addresses in a sentence, whether specific or not, a comma should be placed between the street and city, between the city and the state, and at the end of the address.
EXAMPLE: Use the address 5401 West 20th Street, Greeley, Colorado 80634, for any mail
When using a specific date in a sentence, a comma should be placed between the day and the year and also after the year.
EXAMPLE: August 22, 2011, is the day I began my first semester of college.