The comma [ , ] is the most common punctuation mark in English.
Most writers take one of two attitudes toward the comma: commaphobia or commaphilia. The commaphobe dreads and fears the comma and tries to avoid using it at all costs. The commaphile adores the comma and uses it incessantly, mostly for decoration.
The cure for both of these unfortunate conditions is knowledge. Once you master the hows and whys of comma usage, you can stop either avoiding or embracing commas and simply make use of them.
Unfortunately, there are lots of rules for using commas. Writing handbooks usually list all of them. Such lists, paradoxically, make it harder to figure out how to use commas correctly.
Here are five rules that will cover most cases: