A fantastic photographer, devoted to Photoshop, once said to me, “Yeah, I love Photoshop, but I really don’t use Layers.” I was agog. This is sort of like saying you love to cook but stay away from pots and pans.
Layers aren’t just for making composites and doing collages. They are important tools that afford you very fine control over the way you edit your images.

Photo: David Yu (Click for a full-res image)
Using Layers, you can control the amount of every change you make, double up on some edits and remove others, and carefully address small areas of your image—all while leaving your original image intact. And you can do far more with Layers than just duplicate them and delete them.
What follows are five tips for working with them in a more nuanced way. Some are great for users new to the tool, and a few are more sophisticated.
FYI: Layer keyboard Shortcuts
If you make a selection on any layer, you can quickly copy and paste the contents of the selection to a new layer by typing Ctrl (Command on a Mac) + J. To merge the selected layer with the one below, type Ctrl + E. If you want to merge a bunch, Shift + click on them all and then type Ctrl + E. To make a selection around all the contents of a layer, hold down Ctrl and click on the layer thumbnail.