I'm going to follow this rule of thumb: use normal travel rather than fast travel if I haven't yet traversed the route *in that direction*. That way I'll usually end up seeing an area both coming and going at least once.

I expect this will get me a better sampling of the random encounters in a region, not to mention enjoy the vistas from more angles.

Also -- if I were a map designer and I wanted to make a path / hole in the ground / shrine / etc hard but not impossible to find, I would put it out of sight of anyone traveling *away* from the nearest major city, but noticeable by anyone traveling the normal way back.