Layer masks in Photoshop Elements

Layer masks are useful, but I don't use them often enough to remember how to implement them every time, so I'm writing this down once and for all here.

A "mask" is something that decides which parts of a layer are shown and which are hidden. So if you have a colour layer in front of a B/W, you can use a mask to define which parts of the colour layer are shown, and which aren't.

Instructions at: http://www.essential-photoshop-elements.com/layer-mask.html

In short:

1. Create new adjustment layer
2. Position adjustment layer between layers
3. Select top layer and group with previous (which is the adjustment layer)
4. Paint with black on adjustment layer to hide areas of the top layer