While there are many specific uses for commas, nearly eighty-five percent of the commas used in written English are used in a mere three situations.
If you know the basic rule for these three cases, you can use commas in over four-fifths of the times you need to use commas.
1. Put a comma before a coordinating conjunction that separates two independent clauses.
2. Put a comma after introductory words, phrases, or clauses in a sentence.
3. Use commas to set off elements that interrupt or add information in a sentence.