Actions are wonderful as a shortcut to anything you frequently do in Photoshop with multiple steps.
Here's how to create an action that duplicates a layer
1. Choose a file or element from your stash. (If your file has multiple layers, make the layer you want to duplicate active)
2. Choose Actions from the top pull-down menu.
3. Click on the CREATE NEW SET button
4. Name the set something like My Action Set
5. With your new Action set highlighted, choose the CREATE NEW ACTION button
6. Use these settings in the dialogue box (or choose your own Function key and modifiers)
7. Click OK
8. Choose Layer/Duplicate Layer from the top pull-down menu
9. Choose NEW for the location than click OK Type a name (optional)
10. Click on the STOP RECORDING button
Now anytime you want to duplicate a layer as a new file, just use your new shortcut.
FYI: Be careful that you are not overwriting a keyboard shortcut that uses a Function key (example: F1 F2 F3)
Actions will wipe out any keyboard shortcut that uses the same function key and modifiers.
Useless information: I like to use this action when I have a large number of layers and I want to place a copy of that layer multiple layers away.
Easier to duplicate the layer to a new file and insert it where I want it than to make a copy and and drag to its new location inside the layers pallet.
More useless information It's a snap to create an action to make your layer a smart object. Just follow the same rules as above. You can use the same Action Set you created, click on it to choose it then follow steps 5-10
Let us know what time-saving actions you create!