I have comma problems. I have tried to figure out for years how to use them. I've read many a chapter on how to use commas in many a grammar book, but little, if anything, stuck. However, I have finally found something that has helped: the chapter on commas in Eat, Shoots, and Leaves by Lynne Truss. (I discovered the book by reading earlier posts on this very blog.) She explains the history of commas (did you know the Bible was originally written without commas?) and that many famous fiction writers break the already flexible rules about commas.
Here is a fun little video for anyone who does not want to do the reading.