By creating a tilt shift scene you will learn how to create layer masks and understand how they work. Also you will learn to use the gradient tool in Photoshop.
There are several tutorials we can follow to learn the same technique. In Photoshop you will learn there are different ways of producing a desired effect, it just depends on what works for you. I will walk you through the tutorial and show you the steps involved. If you want to check some of these tutorials out for yourself check out the links below.
Use your brain and photoshop to produce diorama illusions on PSDTUTS.com
Fake Model Photography on Receding Hairline
Making Fake Miniature Photos on Still Scripts.com
Tilt-Shift Photography Photoshop Tutorial