Add two or more drop-shadows to an element and use different values for each.
Layered drop shadows can help make your shadows richer, more complicated, more natural. In the example below I’ve added a second drop shadow which is closer to the element and darker, which some consider to be more natural. You can add many more drop shadow layers and tweak them to get the desired effect.
Each drop shadow you add will make the shadow darker, so be careful you don’t end up with a less subtle shadow than you should have.