Joe Walter's weekly post is up. I probably should take his advice to heart. What matters is that my prose is intelligible not that it strictly follows grammatical rules. I'm going to have to repeat this to myself a lot.
I wasn't really a writer in high school, I was a math and science nerd. But I read a lot. Some of my friends were trying to become writers. I had a teacher in high school that gave writing instruction. He had written several books on writing with an emphasis on fiction, yet to to my knowledge he had never actually published a novel or even short story in his life. The conclusion they reached was that Dr. G. was full of crap. If you want me to read your book on writing, you need to prove what a great writer you are first. Otherwise you are just laying down rules that prevent people from finding their voice.
By the way, why can't you end a sentence in a preposition anyway? It seems to me that rewording those sentences just makes them more convoluted.