Depends on how you're going to use the hexes and at what density. In general, hexes are just a different kind of grid, which you use to determine the general form and layout of an area. If you're using it for wargaming, you have to decide whether you're going to put rivers at the borders of hexes or not - which determines the overall level of abstraction of the map.

In general, hexes are a really cool and simple way to make pretty useful maps for wilderness adventures. I really should do one again ...