Pascal offers some good advice, and I'm going to piggy back on that a bit
.
I don't know what focal length lenses you are using, but to minimize the hazard of camera shake (unless you are using a tripod or have lenses with IS or VR) - you want your shutter speed to at least match the FL. For example, if you are using a 135mm lens, your shutter speed should be at least 1/125 second.
That is also a very good suggestion about being in either MANUAL exposure or some sort of Shutter Priority where
YOU lock in the specific shutter.
In "P" mode or AV you won't know what shutter speed the camera will select until it's too late. If it selects too fast a shutter, all movement will be frozen and you will have lost any sense of motion. Too slow a speed and everything will have some blur. This can be good for rolling shots, but YOU want to be selective and not leave it up to the camera. - Stu