Control/Command + left-click with the Move tool selected and, in
most cases, you’ll select the corresponding layer of the element that your
mouse is over (unless Photoshop can’t distinguish between the multiple
layers).
Yo u c o u l d a l s o Control/Command + left-click on a layer’s miniature
icon to get a selection of the content of that layer. The marching ants will
show you what is on that layer and where it is.
Another option is to click on the Layer palette’s Options icon, in the top-
right corner, and select “Layers Palette Options.” From here you can adjust
the size of the layer’s miniature preview and concentrate the miniature’s
content to the layer’s bounds, which should cut down on future guesswork
when it comes to layer contents.