Understand conventions for using commas and appreciate the likely effects of particular sentence lengths and patterns on reading comprehension.
Commas are like pawns in chess: They seem relatively insignificant and unobtrusive, yet they are actually very important. If properly placed, the lowly pawn can checkmate the king or, once it has reached the end of the board, become a more powerful piece.
Commas play an extremely important role in ensuring that your documents are understandable. In fact, failing to insert a comma in the correct spot can cause considerable misreading (and subsequent embarrassment). Beyond a few special circumstances, there are six basic ways to use commas correctly.