Create Reflections?

I’m going to assume that you’re doing this reflection effect to a landscape or cityscape photo, but you can also use this on everything from people to products. For a landscape photo, here’s what I would do: Get the Rectangular Marquee tool (M) from the Toolbox and make a selection that goes from the horizon line all the way up to the top of the image. Now, press Command–J (PC: Ctrl-J) to put this selected area up on its own layer. Next, press Command-T (PC: Ctrl-T) to bring up Free Transform, then Right-click anywhere inside the Free Transform bounding box and, from the pop-up menu that appears, choose Flip Vertical to flip the image on this layer upside down. Press the Return (PC: Enter) key to lock in your transformation. Now, switch to the Move tool (V), press-and-hold the Shift key (to keep things perfectly straight as you drag), then click-and-drag this flipped layer down until the top of it touches the horizon line in your original image, and that creates the mirror reflection. That’s all there is to it.