Traveling over land, what might be a good route

In the modern times, a road is generally a good option.

Before the roads were build, following a river would make it easy: it would ensure that you most likely won't encounter a big mountain on your way.

If you can't find a river and there are no mountains in sight you might choose just a steady ground, but if there are mountains in sight, using valleys and going along valleys might be a good option.