This week's challenge at 2Peas is how to work with shadows. Kate Teague uses a method I haven't tried yet: duplicating the element, changing it to dark brown, then using the warp tool to drag it around until it looks right. Here's how I did mine:
Extract your element, then give it a drop shadow in the layers palette. Now, right-click on the little eye symbol on that layer, and choose "create layer". Now the shadow is on its own layer, and you can transform it any way you like! Ctrl+click on the thumbnail of the shadow so that the entire shadow is selected, then go to Edit-->Transform-->Perspective. You'll see a transform box come up, as usual, but when you approach the corners and mid-points, you'll see that your cursor changes to some different arrows. Play around with it a little, and you'll see the shadow elongate and get skinnier up on top, as if it were receding in the distance. You can apply the effect, and also go back and choose the Skew function, which will keep the same proportions, but move the shadow side to side or up and down, changing the slant of either the horizontal or vertical axis.
Once I'd finished messing around with mine (make sure the shadow originates with whatever touches the plane your object is sitting or standing on), I realized it was too dark, so I lowered the opacity and put some Gaussian blur on it. Et voilà!
Another option is to use the warp tool (Edit-->Transform-->Warp), especially if you want to move your shadow into curved shapes (perhaps you're following a bumpy surface, for example), so just pay attention to what your object's relationship is to its base and background.
Do click on the image for a larger version and to read the journaling...