I like to set my books in real cities because I believe readers relate to places they know, live, or have visited. My cop series is set in Wichita, Kansas, which is a large enough city that they probably have plenty of crimes and good cops to solve them. Actually, around the time I was writing the first book, Family Secrets, the BTK killer had just resurfaced in Wichita and was soon apprehended. I added a mention of him, a "Did you work on that BTK case?" type of thing, for a touch of realism. But that's as far as I went with him. His crimes were horrible and touched the people of Wichita deeply. I didn't want to remind them too much.
I asked several people from the Wichita area about neighborhoods, locations by the river, various aspects of the city that I could include. I tried to steer clear of actual addresses because I didn't want a reader saying, "That's my address in Wichita!" And that's the very reason I make up business names, Like Moe's Diner and Sister Theresa's Shelter. If I wanted to make Sister Theresa the bad guy (or nun, so to speak) in the end, I didn't want the real Sister Theresa saying, "Hey now!" So while the story is set in Wichita and a few of the main streets are mentioned, as well as neighborhoods, the rest is purely fictional. Recently a reader told me she was from Wichita and while I changed the names, there was indeed a diner and a shelter like the ones I wrote about, and she could picture them as she read.
My Witness Security series is set in Topeka, but the city won't play a major role. These people are in hiding and generally aren't going to be out doing the town. They'll also be traveling to other locations, in the first book they went to Chicago. Book two takes the characters to LA. Both towns I've visited and hopefully am able to capture their essence.
I took a different tactic with my Blame Game series, creating a fictional town for the characters to live in. I had a certain real town in mind and gave the fictional town of Marshall features of that place I knew well, but I had the freedom to jiggle them around as I desired. What I like about a fictional setting is as long as I'm consistent, I can create any details I want. No one can write me and say, "Excuse me, Fifth Street never intersects with Prospect Blvd." In my fictional town, maybe it does.
Find the first book in each of my series' here:
Family Secrets, A Cop in the Family: http://amzn.com/B004478IN6
Pieces of the Past, Witness Security: http://amzn.com/B00K5XAGY2
Blame it on the Stars, The Blame Game: http://amzn.com/B00EOA5G3I