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).
A MORE 100 various with denser meaning than simply using "GOOD". Expand your vocabulary to more efficiently and quickly and accurately (and when appropriate using these appropriate express the concept of one client to another/others.