Multiple light sources ... AAAAAAAAGGHH!!!!

What's your worst enemy in post-processing? Noise? Nope. Underexposure? Nah. It's multiple light sources! I hate them so much!!!!! Well, let me clarify. You can take a photo with as many light sources as you like, as long as they're exactly the same temperature. But if you have a photo with two or more sources of different coloured light, it's a nightmare to edit. Usually the problem arises in photos which are taken indoors, with an overhead light and a window providing the illumination. The bulb light is quite yellow, and the natural light is bluer by comparison. If both the warm light and the cool light are striking the subject's face, it's bloody awful to try to balance. I'd rather edit an underexposed, noisy, yellow photo over a perfectly-exposed, clean photo with two light temperatures. One white balance problem is easy to fix; more than one in the same photo is very difficult. So, make things easy for yourself. You can shoot in natural light, or fluorescent light, or tungsten light, or whatever ... just make sure there's only one light temperature. You'll save yourself plenty of headaches back at the computer.