How do you not get lost following a footpath for hundreds of miles? Staying alert will help, but the trail is marked with white blazes. A single blaze means your on the trail, a double blaze is an alert that the trail is going to turn. Sometimes they even offset the double blaze to indicate the direction of the turn. It seems like I am in tune with the blazes because many times I will be looking at the trail and then look up to see the blaze.
The kids are really good at finding blazes and are getting to the point it is natural for them to anticipate the trail. Harvey used to get confused on side trails, now he is very aware of the trail.