* Start with a photo that has a well-defined foreground, middleground
and background, with something from the foreground near the "horizon
line" (doesn't have to be smack in the middle, but along the midline)
of the picture for best results.
* An example of a good photo to use would be a photo of buildings and
traffic on the street taken from a 3-4 story window, with a car just
getting ready to go through the light in the center of the picture.
* Photos of things we identify as "big" work best -- buildings,
trains, traffic, etc... Things that are smaller or of indeterminate
size are more difficult to make convincing miniature pictures with.
(Probably a big "duh," here, but I have had students try to
miniaturize each other with vague backgrounds, or iPods, or
whatever... and it doesn't work. If you really want to miniaturize
your friend, have him stand beside a building or tree or something.)
* It is really cool to miniaturize a scene that isn't perfect -- a
building with a boarded-up door, or a shop that has been vacant for
years. Little details that let the viewer know that this is probably
not a real miniature make it interesting, especially if you can get a
really good tilt-shift effect.
* You might also want to experiment with the amount of blur you use.
* Adjust the color saturation to make the colors a little brighter
than normal to really make the photo look like a convincing miniature.
* Some images just work better than others, so take some time to experiment.
In other words, experiment, experiment, experiment! It's not a
difficult effect to master, but the more you experiment, the more you
can refine the technique to get a convincing miniature scene. (I had
my principal believing that I had built a miniature Nashville in my
basement. She was floored when I told her it was a Photoshop trick!)