I recently bought a gently used copy of a common style manual which I will be spending a large part of this week learning. (Aside: If you want to save money on a style manual, buy it used from eBay.) There is a wonderful PDF presentation on the internet (“internet” is lowercased according to The Chicago Manual of Style 17th Edition, one of my favorite manuals) called “How to Learn a Style Guide in 10 Days,” which is highly useful for learning the style manual of your choice. It can be found at https://askcopycurmudgeon.files.wordpress.com/2012/11/learn-a-style-guide.pdf
For an editor like me, who specializes in scientific manuscripts, being proficient in more than one style manual is very important. Scientific journal publishers tend to want manuscripts to conform to either the Publication Manual of the American Psychological Association (APA) or the AMA Manual of Style (AMA). Some publishers even have their own style guide. APA is now on its 7th edition and AMA on its 11th. CMoS is on its 17th edition, as I noted above, and just about every editor should know CMoS because it is considered the “gold standard” of editing, and is defaulted to whenever another style guide has not been specified.
My copy of the new-to-me style manual which I will be learning for the next 10 days is currently sitting on my desk, having arrived less than half a week ago. I cannot wait to crack it open and begin developing proficiency; I will begin tomorrow, since Monday is a good day to start things like this. Personally, I love how the style manuals all have their different nuances and guidelines for things such as the treatment of numbers in text (do we write out one to ten or use the numerals 1 to 10?), capitalization (do we capitalize “Internet” or leave “internet” lowercased?), and closed versus open compounds (is it a “bar stool” or a “barstool”?). If the guidelines in every manual were the same, the world would be a dull place.
If you are an editor or writer, how do you best learn a style manual?