Autofocus Continuous mode would be my choice, meaning that the camera will shoot a shot whenever you press the shutter release firmly; there's not much worse than having an AF-Single or AF Focus Priority custom setting turned on, and being forced to watch a potential photo opportunity go by because the camera's AF system thinks the focus is not 100 percent dead-on.
Different camera makers refer to this mode using different terms. I suggest AF-C in Nikon, with the sub-menu in more advanced cameras set to Release Priority, not Focus Priority. That way, whenever you want to press the release and shoot, the camera will shoot.