Quote Originally Posted by .sarah
There are lots of shots I have with the dogs coming at me at full speed and I have their chests in focus because I just couldn't focus and click fast enough.
Does your camera have an 'Al Servo' focus setting? My XTi has that and it continues to track the focus right up until the shutter opens which means it should have a moving object in focus. It eliminates being able to do the focus lock and you have to keep your subject in the center but if it's a matter of getting the shot or not you could always crop it later.