One third of our punctuation marks are commas.
Commas are important.
They are as important to written communication as pauses and pitch variations in voice are in verbal communication. Often commas are used in writing where a pause would occur if the same sentence were spoken. The accurate placement of commas is determined by specific rules. Although comma placement depends upon the grammatical structure of the sentence, the comma is, in the final analuysis, a tool for the writer. He should not only know the comma rules, but also should always make sure the commas he uses have aided in his effort to communicate accurately and effectively with his reader.