1. Open a new document, whatever size you want.
2. Create a new layer with a transparent background. In this layer, draw an object. I chose to draw a bird, which is actually a shape, not an object. If you go this route, you must make this shape into an object. To do this, select the layer with the shape and go to Layer -> Rasterize->Shape. Done.
3. Duplicate Layer 2 with the object.
4. Select Layer 2 again. Lock the transparency by selected the small checkerboard icon in the layers pallet.
5. Using the paint bucket tool, fill the object layer 2 with black
6. With layer 2 selected, go to edit ->transform->flip vertical
7. Drag the black layer down until the bottom touches with the duplicate layer.
8. Still with layer 2 selected, go to edit->transform->perspective. Now drag the corners to get the desired look you want.
9. Unlock the transparency (checkerboard icon). Then go to filters->gaussian blur. Try using about a 5.
10. Still doesn’t look right change the blending mode to multiply. If there is background color it will add it to the shadow.
11. Now lower the opacity of the shadow layer like to 70 or 80 (select the shadow layer and adjust the opacity in the layers pallet).
Your end result should look something like this:
