Have you ever adjusted your white balance setting on your camera? 99% of the time, I recommend leaving your white balance on AUTO mode, here's why...

I've helped a lot of folks who had a blueish or yellowish cast to all of their images simply by making this simple adjustment — moving their white balance from tungsten, sunny or cloudy to auto. It's a quick fix that will really affect the color of your images.
What's going on with white balance?
It's your camera's sensor trying to adjust for different temperatures of light. For example a room with lamps in it has a very different color temperature than being outdoors under a shady tree — When your camera is set to auto white balance, it will adjust accordingly, to suit the current lighting temperature. Got more than one light source in a single image (for example lights on in a room and natural day light coming through the window)? No problem, auto will still come out way better than trying to decide between tungsten (lightbulb light) and daylight. In this instance, auto really is your friend.
Bethany Nauert, a professional photographer and one of our top tour contributor's at Apartment Therapy had this to say about white balance:
"There is a common misunderstanding about indoor lighting; yes it's pretty to the eye . . . But it is the enemy of white balance. Remember if you're going to shoot a room with lovely warm lights all along the bed side table . . . that warm light will distort the color of the walls, bedspread and pretty much anything around it."
xoxo,
Leela the Photo Magician
Image: Creative Commons by Bruno Girin

Shaw's Original Fir...
It really depends on the camera. Canons have really had autowhite balance from personal experience and from various reviews. For them, you really do get a better white balance if you do condition specific. Its even better if you take the time to calibrate using the built in calibration.
Shoot in RAW, then it doesn't matter! ;)
Really, though, I'd say shoot first in auto, and if the color is awfully yellow or off, try experimenting by going to a different mode if you're on a point and shoot camera. The key is just to remember to turn that mode back to auto when you're done.
Really, it just depends on your camera.
I always shoot WB on auto. It does a really good job and especially since I always shoot in RAW, it's a lot easier to fix any weird hue in post.
For Hobbyists shooting in raw then auto WB is fine. But white balance is one of those things that isn't really THAT hard to not only understand but control. With a little bit of practice and just getting out there and shooting, you'll never touch auto again. Both Canon and Nikon's preset WB's are really good. Just a quick adjustment when you need to and you're good.
Two scenarios when you shouldn't shoot in Auto WB:
(1) During the Golden Hour (after sunrise and before sunset). The camera tries to compensate for the lovely warm light and you don't end up with the photo you thought you were taking.
(2) Under fluorescent lighting. Fluorescent tubes have weird light -- it's not just the color temp that's different; there's a whole different mix of reds, greens and blues that other lighting types tend not to have.
I have an Oly EPL-2 and my autoWB works great! I almost never take it off that, unless I'm trying to get "creative" or "artsy" or whatever.
Fluorescents ARE pretty weird to shoot under, but my auto WB usually does a pretty good job of compensating. If the fluorescent light takes up a large portion of the image or there's a lot of fluorescent glare, I start getting pink/blue/red spots, which means autoWB isn't working enough.
I agree with the premise that 99% of the time, AWB is the ticket!