There's a filter for these effects included since PS CS 6
http://www.photoshopessentials.com/photo-effects/miniature-tilt-shift- cs6/
If you dont want to use these filters theres another workaround. (CS 6)
- Duplicate your backgroundlayer or the layer on which you want to apply this effect.
(convert it into a smart-object, if you want to adjust the strength of the filter at any time)
- Go to 'filters' -> 'Blur' --> 'Gaussian blur'
Set the filter to an amount which works fine for you.
- After you hit OK the whole image will be blurry.
- Now create a new layer-mask for the blurry layer.
- select the gradient tool (shortcut 'G' or 'Shift+G' on your keyobard)
Make sure you have the mask selected. (white border around the miniature of the layer-mask)
- Now set the gradient style on 'reflective' and draw a gradient on that mask.
Hope this helps.