Do not always put a comma where you pause in the sentence – it’s a good place to start but not always correct.
Place a comma:
1) after an introductory word or phrase
Generally, commas are perceived as difficult.
In fact, they are quite simple.
Once you figure them out, they will become second nature.
2) before a conjunction (FANBOYS) that separates two complete thoughts (including a subject and a verb)
I like to read and write. I like to read, and write.
You like to read but don’t like to write. You like to read, but don’t like to write.
You need to know about commas, so I am telling you about them. You need to know about commas so I am telling you about them.
3) NO COMMA SPLICES! (don’t use a comma alone to separate two complete thoughts)
I know you are confused with commas, it isn’t unreasonable. I know you are confused with commas; it isn’t unreasonable.
Comma splices are common, they are evil. Comma splices are common, and they are evil. Comma splices are evil because they are common. Comma splices are common, but they can be corrected.
4) Conjunctive adverbs (not FANBOYS – however, therefore, moreover)
I consider myself good at English, however I don’t enjoy it. I consider myself good at English, however, I don’t enjoy it. I consider myself good at English. However, I don’t enjoy it. I consider myself good at English; however, I don’t enjoy it.
5) commas in a series
There are many rules for commas, semicolons, and colons. There are many rules for commas, semicolons, and, colons.
6) adjectives not joined by “and”
The strange and erratic comma placement was silly. The strange, erratic comma placement was silly.
7) interrupters and emphasis
Mrswho, a girl confused about commas, was needing some help. Fluther, a site where people answer questions, is very helpful.
rules from http://www.unc.edu/depts/wcweb/handouts/commas.html
We now have an acronym – abNCcai. . . er, nevermind :)
I hope this helped!