Show your editor some love, they do a great job remembering you for a story assignment and coordinate details with you for your article, so check out some of these gifts here which I am sure any editor would love to be at the receiving end of!
The majority of my clients - media, individual or corporate, all ask for work to be done following the Associated Press or AP style book. Very rarely have I come across anybody asking for the Chicago Manual Style or any others though there are some folks that try to stick to those anyway. I have been able to do without an actual copy for a year or so now but decided to invest in one this year so I can flip through pages right here at my desk and get answers to my editing queries asap instead of having to search online and see if someone else has had the same problem before. The book is certainly a great investment, I swear by it. It isn't very expensive either - you should be able to get a brand new copy through Amazon for about $20 or so, else rummage through your local book store and you might be lucky enough to find a used copy for so much lesser. Many publications, both print and online, use this as their Bible so it only helps that you are already well-versed in the AP style even before you apply to work with them. Have you had to work with other specific styles for your clients? I'd love to know more.