What do you do when one side of the face is visible and the other is in the dark? Of course, you could hold up a reflector. But if you aren't one of those photographers who have an entourage to do this kind of thing for you, merely having someone stand just outside of your frame wearing a white shirt could do. Someone holding a white sheet could do as a reflector as well.
One of the most important digital photography tips you can have has to do with understanding how pictures taken by digital camera translate between the screen and print. If you have never noticed this before, digital photos look a lot better on a physical print that they do on a computer screen. Part of the reason this is so is that computer screens happen to be a lot bigger than photo prints, and they are lit up. This makes all kinds of digital noise and grain quite apparent on a computer screen that never would be apparent on a print. For this reason, you need to cut yourself a little slack when you try to compare your photos with those in print. Things work out differently in print.
Okay, here's the mother of all digital photography tips if you are looking to photograph your wife or girlfriend to really flatter them. Not that they have any wrinkles, but overexposing your shot by tiny bit (assuming your camera has the manual controls it needs that will allow you to do this) hides wrinkles and brightens a picture up enormously. You could always darken up the places that you wanted on Photoshop. Elsewhere, overexposure really flatters the subject of your picture.