For any one thing you want to do in Photoshop, there are probably at least 50 ways to go about accomplishing it. However, perhaps no tool is more versatile than Curves, which allows you incredible control over luminosity and color and in tandem with masking, can give you tremendous creative editing capabilities, as this fun tutorial will guide you through.
Coming to you from Unmesh Dinda of PiXimperfect, this helpful video will show you how to adjust the lighting of and grade an image using Curves in Photoshop. Most people think of Curves as a tool for adjusting absolute and relative luminosity values, and while it's certainly useful for that, when you move away from the RGB curve and begin adjusting individual channels, you've unlocked the full capabilities. This allows you to quickly and easily add or subtract color to an image based on varying luminosity values with fairly precise control as opposed to some other tools, which makes it my favorite method for this sort of work. As Dinda demonstrates, you can take advantage of this along with some creative use of layer masking to transform an image relatively quickly (especially once you get a feel for the tool's behavior). Give it a try!