One solution strategy that works very well from my experience is to ask them upfront whether they want to play "for real" or to play to learn. [edit: A third mode is "for (silly) fun" where everything is allowed.] This works for all ages... and for boardgames and physical games. It's their choice which mode they want to play in, and they trust and respect you more when given the choice. You treat them as a peer. You…
A common idea in Go is that a stronger player will play a "teaching game" with a weaker one. The game is sufficiently abstract and complex that the weaker player may not even notice the actions of the stronger player who endeavors to play poorly so that they are only slightly better than their opponent and have the opportunity to share new ideas and tricks at a level appropriate to their student. Obviously, these hav…
I recommend to people learning to look at the activities of someone "good" at the field but not a star for this reason, I don't know if it applies to all fields but for ex I got the same feeling learning chess by following GM's games (I was lost) and a book like "Master vs Amateur" opened my eyes to typical errors made by intermediate players that won't show up in chess books (another example is "The Amateur Mind"). I tell soccer players than besides enjoying watching the games of the big teams and star players to watch "journeymen" games from a 2nd division to learn the basics.
Also the reason why we frequently learn more from a student mate explaining something that from a veteran teacher or professor, who forgot the struggles of the beginners.