don’t forget that once you’ve applied the drop shadow, you should go in (double click on the little circle that appears on that layer) and modify the settings. Usually, the base drop shadow is too big for realism. If you double click on that little circle, the layer styles window will open. Click on “drop shadow” and you’ll see the settings. Depending on what you’re apply a shadow to, you’ll want to modify the size, distance & spread until it looks the way you want it to look.