Beyond a list of cities, a usable itinerary shows how many nights each base gets, what happens on arrival and departure days, and how travelers move between stops door to door—not just scheduled journey time.
Build in a buffer day before any long-haul flight home and leave at least a few half-days unscheduled. An itinerary that survives one delayed train or closed museum is more useful than one that only works if everything goes to plan.