Step 1
Create a new document 600px * 600px at 72dpi as seen below.
Step 2
Then create a new color fill layer by going to LAYER >> NEW FILL LAYER >> COLOR in the menu and choose the value #000000 as shown below.
Step 3
To add some lighting to the background first rasterize the color fill layer you just created by right clicking on the layer and choosing RASTERIZE LAYER . Then add the by going to FILTER >> RENDER >> LIGHTING EFFECTS in the menu and entering the settings below.
Step 4
Now lets create the circular base of the icon. To do this activate the shape tool by pressing U. Make sure the circle tool is selected then draw out a circle similar to the one shown below.
Step 5
Activate the layer styles pallet by going to LAYER >> LAYER STYLE >> BLENDING OPTIONS in the menu. Then enter the settings below.

Step 6
To create the shadow that helps give these icons their 3D look first create a new layer beneath the square layer you just created. Activate the brush tool by typeing B. Choose a simple round brush, set the opacity to 50%, the size to 25, and the sharpness to 0, then paint in a rough shadow around the base of the icon as seen below.
Step 7
To clean up the shadow first apply a motion blur filter by going to FILTER >> BLUR >> MOTION BLUR in the menu and entering the settings below.
Step 8
To clean up the shadow further apply a gaussian blur filter by going to FILTER >> BLUR >> GAUSSIAN BLUR in the menu and entering the settings below.
Step 9
Now above the square layer create a new layer by going to LAYER >> NEW >> LAYER in the menu. Activate the shape tool by typeing U. Make sure the custom shape tool is selected then choose the built in check mark shape and drag out a shape similar to the one below.
Step 10
Activate the layer styles pallet on the checkmark layer you just created and enter the settings below.
That's it!
You should now have something like what you see below.

