from Receding Hairline:

With a very little effort, you can take existing photographs of everyday scenes and make it look like they're actually of miniature models.

It doesn't take much to fool the mind of the viewer, but there are a few basic rules you can follow to help convince your audience that they're looking at a railway set rather than the real world; see the section on picking the right photo at the bottom of this page. You'll need a copy of Photoshop CS or later to follow this tutorial.