Step 1.
Open an image you wish and apply View > Show > Grid ( Ctrl+Alt+'). Choose the Polygonal Lasso Tool and create a polygonal selection.
Step 2.
Create a new layer and fill it by 50% Gray (apply Edit > Fill). Now you can turn the grid off (apply View > Show > Grid or press Ctrl+Alt+'). Deselect the selection (apply Select > Deselect or press Ctrl+D).
Step 3.
Apply Layer > Layer Style > Stroke to a new layer and use the following settings:
Apply Layer > Layer Style > Bevel and Emboss with the following settings:
Step 4.
Set the Opacity on the Layer palette to 50%. Now you can create several "polygons" like shown in the pic.4. And that's it.
More Tutorials: 
