A review of the basics is always beneficial. This poster, created by the folks at www.knowledgeunlimited.com, measures 18- by 25-inches. You can order it for just under 15 dollars at http://www.thekustore.com/kucatalog.cgi/7124P
The Seven Deadly Sins of Punctuation And How You Can Avoid Them (Note: Read carefully. They preface each "faux pas," telling you the correct usage, but provide the WRONG way as examples. It's confusing).