If you have multiple shapes that each have a drop shadow layer style applied and you want to change the angle of just one, do the following: Double-click on the layer in the Layers panel to open up the Drop Shadow options in the Layer Style dialog Deselect Use Global Light Change the angle to whatever you like
I believe that @Myra Ferguson has provided the correct answer! Please mark it as so if it solves your problem.
On a side note, it would be nice to have a keyboard shortcut to remove the global angle from an active layer. I have been hacking at some SL code but I can't get it to simply uncheck the global angle without affecting any other parameter. Perhaps somebody with deeper knowledge of AM scripting can offer something?