Like everything else these days, even socks have become high-tech. There are a number of factors to consider when buying socks. First, there's the material. Wool has the best insulating ability, yet it still wicks sweat away from your feet effectively. If your feet are on the sweaty side, a synthetic sock is the way to go.
Synthetics do a better, faster job of wicking away that sweat.
Next check out the density of the fabric, whether it be wool or synthetic. The rule of toe is the denser the better. Turn the sock inside out and inspect all those little fabric loops. The smaller and tighter and more dense they are, the more cushioning that sock will have over the long haul. Also, check out the thickness of the socks and try them on with your hiking boots.