DittoI have to agree with @filbert ; county road access. The headaches from dealing with neighbors over shared privately maintained roads is a major problem. If you must be on a private road, at least be the closest one to the County maintained road.
Live water will thin the choices dramatically. Also, if you are on live water, be on the inside of the curve of the river. The outside of the curve means the river will eat your land every flood. I've seen many, many acres just disappear to the water (look up Twin Lakes, south of Crescent and west of Guthrie).