Angles on the field. An example would be does the third baseman have trouble throwing across his body? My son bats left. Through high school if he saw this and was played like a pull hitter he dropped a bunt on the line. Free hit.
Another thing to watch is do outfielders get behind flies?If not, they won't have momentum coming forward on a tag. They may even be on their heels. Do they take proper angles on singles? Would it be easy to take two bases as a runner. It's easier to coach a base when runners have good instincts and are aggressive because they've picked up the little things.