I'm a little more limited than most with regards to this question: the setting for most of my fiction books has been decided by my editors. This has resulted in some interesting scenarios: for instance, having to write about California, when I've never been to California. I had to set an entire book in a vineyard in Napa Valley. Not only have I never been to Napa, or a vineyard, I didn't even know what grapes looked like when they were growing. Thank you, Google Images. I also got around this particular problem by renting old Rick Steves Travel DVDs of Napa and looking through big coffeetable books about life on a vineyard.
Then there was the book that was supposed to be set in Palm Springs, CA. Fine, no problem, I told the editor. I've got it under control. Off I go, writing the manuscript. I was used to writing about California by now, and my characters always spent a lot of time at the beach. So I wrote in several key beach scenes, as usual. Oops. I later was informed that Palm Springs is like miles and miles from the beach. It's in the middle of the desert. If this isn't a testament to the value of research, I don't know what is. I had to rewrite every d**n one of those scenes.
That's a big reason why setting Hard to Get in the Midwest was such a relief. At last, I could write about a terrain I was familiar with: daffodils in spring, changing oak trees in fall, cornfields, soybeans. The book I'm working on now is set somewhere in upper Michigan. My best friend's family once owned a vacation house there that had been in their family for generations. I only visited the place once but I've never been able to get it out of my mind. Something about the loons. . .