Is it affect or effect? Lay of the land or lie of the land? Learned or learnt, or are both acceptable? Wreak havoc or wreck havoc or work havoc? Must you rely on a search engine and website of unknown repute to find out?
I'm finishing the last of four courses for a copyediting certificate, and one of reference books we're using is Garner's Modern English Usage. If you're serious about using exactly the right word, or want to know which "rules" are really superstition, or want to know what zombie nouns are so you can avoid them, and so on, then this is a good book to add to your library.
Have you ever used a usage guide? Are there any commonly misused words or phrases that you have trouble with, or that are a pet peeve when someone else uses them?