If there's anything that marks a person as a new or inept speaker of English, it's the misuse of prepositions.
For example: There is something wrong of my car (newbie error). Or Where is my car at? (inept usage).
David Thatcher calls them "the banana peels of modern speech." He refers, also, to the prepositionally problematic phrase "fooling around on [one's] wife." Even better, he does this with a British accent. Now a retired English professor, he presents a downloadable guide called "Saving Our Prepositions."
You can find it here. SPOGG is grateful, delighted, and amused. It's quite good, and almost certainly the only language manual that makes any sort of reference at all to the beauty of the word "gonorrhea."