Drop shadows must be applied to raster layers. If you are working with a vector object, you will have to convert the layer to raster in order to apply any effect, including drop shadows. No matter how you make your selection, though, the same principles apply. The first thing, in my opinion, is to understand that a shadow can do damage to your image. They must be carefully planned and adjusted to achieve a great look.
Many people use only default values to apply drop shadows.
This is a serious mistake, since the default values are almost never a good choice for any object. Almost all programs offer defaults that are too dark, or two defined. Look at the sample at the left to see how much you can improve the look of a shadow by changing a few values. Although most of you will know how to apply a shadow, let's start with a quick rundown. There has been a small change in how shadows are applied between version 6 and 7.