TIP: Give your sky some pop

If you'd like to add a little more "oomph" to the sky in your photo, try this: make sure your foreground color is black and add a Gradient adjustment layer. Choose the foreground to transparent gradient and make sure black is at the top of your photo (check the reverse box if black is not at the top)
Change the blend mode to Overlay and your sky will get that extra pop.
(With the Gradient Fill dialog open, click and drag on the photo to change the "length" of the blend)