People are among the most important and enjoyable subjects to photograph, but portraiture can also be very demanding. People get anxious about having their pictures taken and downright upset if those pictures aren’t flattering. A little Photoshop magic can alleviate a lot of that stress.
Before you even begin editing the original, you should save a new copy (File > Save As in any application). Why not just create a duplicate of the original layer, leave it untouched, and keep everything in one file? Because there are dozens of actions you can take that’ll inadvertently affect both layers—cropping, for example, crops all layers. Remember, when it comes to photo editing, irreversibility is the devil, so work with plenty of copies.