Deidre - great topic! As a new publisher, I have battled with this very thing over and over again.
AP styles is good to follow although, in my opinion, if you want soul or a personality in your writing, don't stick to the AP styles strictly - but then again, just my opinion from what I have learned.
When we did our first teaser issue of id Magazine - I let an Editor-In-Chief from the newspaper world run and deal with all of the writers and written content.
After picking up that magazine, and reading it as a reader, I was not exactly happy. (During production, I had no time to actually read the articles) There was no personality, no opinions and lack of any sort of pizazz. Yes, my fault, but it was a lesson learned for sure.
Because a newspaper mind was running that, and not a magazine mentality - we lost the writer's voices along the editing process. Magazines are quite different, you do pick them up to get opinions and such. Newspapers present facts and mostly just that.
Unfortunately, I fear Dennis' statement to be true, "Nowadays, standards are so low and really good writing so rare that it seems to matter little." A lot of writing you pick up today is so, how shall I say? Dumbed-down! 6th grade level I think is the norm in newspapers - I could be wrong.
I'm going to check out Judy's suggestion, "Elements of Style" - and see what I can pick up from it.
Good luck to you!