It isn’t facts. It’s knowing which morning to change the plan, and saying nothing about it.
Ask most people what makes a great guide and they will say knowledge — the dates, the names, the history. Knowledge is the floor, not the ceiling. The guides we keep are the ones who read the day, not the guidebook.
A great guide knows which morning to quietly change the plan because the light is wrong, or the crowd is large, or you slept badly and need an hour more than you need a fortress. And they do it without announcing it, so the better day simply seems to have happened to you.
That is the craft: not telling you everything they know, but knowing which one thing you need right now — and arranging the day so you never see the work behind it.