I program the entire route as one segment, because I can see the entire route on my (GPS)topo map, just as if I had it in my hand in paper form. So there aren't any hidden spots to fool me. Even though I can see the GPS straight line a segment, I can also see the trail and its irregularities as well. Typically when I use the GPS, I don't have it directing me, I just hike, and track my progress via the real time data and topo overlay. Then I see my track intersect waypoints on the route. These waypoints are usually put in as direction indicators, ie, turn R or L, head off trail, possible campsite, possible fishing spot, creek ford etc. If I was to see my track veer off of the route, then I would double check to see why I wasn't on my "route" or trail, and make corrections. This can happen at a junction where the visual direction may be a bit confusing until a short distance is traveled to verify you are on the right track. Like when two trails head off in the "same" direction...