Any design gains realism by the addition of strokes and shadows. I used to spend hours working with these features, but thankfully Photoshop's layer styles now take away that burden.
Here's my favorite trick for using styles: Whenever you have a design that you think looks dull, double-click to the right of the layer name. In the Layer Style dialog, select Drop Shadow or select a stroke (see Figure 4). After selecting a style, move back into the illustration. Notice that you can move that drop shadow or stroke in real time. This feature usually adds interest to a graphicit hasn't failed me yet.