I ran across this website a few weeks ago and forgot about it until I had to add some apostrophe action to a recent press release. Instead of asking around the office, I returned to this cartoon flowchart and found my answer.
Apostrophe.me has an illustrated guide that covers just about any question regarding placement and usage of the apostrophe. It’s very helpful and has some pretty funny examples too (Bob’s bacon hat is the best). The image links you to proper possessive and plural placement of apostrophes. Next up, Altruistic Alliterations: The Layman’s Log!