Do they simply follow in a straight line, in the middle of the lane, keeping the same gap length? Or maybe they are always on the outside of a lane, away from oncoming traffic, never trying to look past the vehicle ahead? Or maybe they move freely in their lane, consciously trying to see traffic farther ahead?
The first two usually indicate less awareness and skill, while the last one indicates more. With just a couple of seconds of study, it’s usually possible to determine what type of driver they are. Combine this with continued observation and you can most often predict their actions, which allows you to better time yours.