If you are imagining some different locations though, there are some things that it's useful to think about. Why that location? What will it give to the story? If it's a universal story that could be set in any location, could your choice of setting still bring something extra, to add another dimension? Are there some things that your book has to have, that will give you a lead on where it should be set?
- Weather. I'm notorious for liking to set my books in sunny places, although I had to compromise on that for the Christmas book and introduce a freak snow storm. Or did I? The thing about being an author is that you can make your own weather, within reason. Even so, logic suggests that you chose a place that fits. Readers have expectations - Christmas means snow and summer holidays mean sunshine - but it can sometimes be striking to play off contrasts and disorientation. Evil events happening in glorious surroundings, Christmas in a hot climate, a love affair where it's always raining.
- Knowledge of the location. Intimate knowledge of a place can add a lot to a book, think of Donna Leon or Phillip Gwynne Jones who depict Venice with an insider's eyes. Can you provide that kind of insight? If you can't, the arrival of the Internet has provided all sorts of opportunities for research that were un-dreamed of even twenty years ago. You can find virtual tours of all sorts of places. It just takes a bit more effort to make sure that you have things right. But writers love research ...
- Scenery - nice to look at, but also useful, for getting your protagonists lost and/or stranded, disposal of bodies, stirring memories, fish out of water scenarios, giving that romance a little extra push.
- Atmosphere - what does your location have that could make it useful? Does it have museums and galleries that feature a particular artist who might be special to your protagonist? Are there folk traditions and legends that enhance a spooky vibe? Standing stones? Beltane fires? If you've read Mary Stewart's Wildfire at Midnight, the Isle of Skye plays big part in that story.
- Contrasts - a spin off from weather. What do you have that you can play with? The contrast between a summer street and the cool of a church, between the hubbub of a city and the silence in the middle of a wood.
- Specifics - is there something that your plot is going to need? If your protagonist is going on the run, somewhere with good transport links might be essential to start with. I set the opening of Never Coming Home in America, because I wanted a car crash on a road which you might expect to have very little traffic - in this country that might be a bit more problematic.
- Buildings - Public and private. Is your plot going to need secret meetings where the anonymity of big buildings that are open to the public would be useful? Or do you want a setting where everyone knows your protagonist and they are either sheltered or stifled by it?
- Using your setting against the protagonist. Does your location have the potential to make life harder and increase tension? Torrential rain, remote location - an absolute Godsend to harassed authors trying to sabotage a mobile phone signal that would have finished the plot in five pages! Dropping the protagonist in an unfamiliar place can be fun too.
- Are you going to enjoy writing about this place? You are potentially going to be living there, on and off, for many months. You could pick somewhere you feel comfortable, where the food, the scenery and the amenities are things you will get satisfaction from describing. You might choose somewhere that will challenge you, and if it's crime, somewhere not so salubrious - but it's good to make sure that you know what you are getting into from the start.
- Can you do the setting justice as well as making it work for you? Is the research going to be too much? Are you going to be tempted to provide too much information? A well chosen location can add another dimension to the book, but it doesn't have to become too dominant. On the other hand it can be frustrating to the reader if a book is supposed to be in a specific place, and the author doesn't provide those little touches that set the scene.
I hope these points are useful - they are only intended to be things to kick off ideas. Personally I think the most important thing about writing is being absorbed in your story and enjoying it - at least most of the time. I'm sure enthusiasm comes over to a reader. And if you can add to their enjoyment by the setting for your book, that can only be a good thing.