A Primer on Shooting in Manual Mode: Aperture, Shutter Speed, and ISO [video]
I know almost no professionals who shoot on manual mode outside of studio settings. The computer is almost always better at guessing things like light and temperature. The only time manual mode is used is when you're in a studio where light, movement, etc are controlled.Instead, shoot on aperture mode. Adjust to your desired depth of field according to the ambient light. Use ISO setting to adjust further for light. Finally, when you see the camera is under/over exposing, use the built in exposure compensation slider to adjust for lighter or darker pictures. Pay attention to and trust your exposure histogram.Now you can very quickly (I can't stress how important quickness is) adjust for the perfect picture. And when the action changes, you'll know quickly which of the three knobs you need to turn.Leave manual mode for the studio.