I used to leaf through portrait galleries on line, not necessarily to get exact locations, but to get an idea of different places that look good in photos. I live in a rather rural area in Michigan, so access to barns and fields is easy. Cityscape type pictures can be a little harder to come by, anything that doesn't look like redneckville, USA but if one wants to bad enough, you can drive 45 minutes and get to somewhere a little more urban and populated.
I don't drive around specifically to find shooting locations, but I have to drive around quite a bit for my "real" job so I make mental notes about different places, how they look in general and also during different times of the day. When I get a request to do a specific type of portrait with a specific type of backdrop, whether it be in front of a barn or a pond or a fence, I can come up with something in a day or so. You really need a place that looks unique, is safe, with a suitable area to shoot portraits. Typically something without too much distracting background or things that don't fit in with the rest of the background.
Best of Luck to you!