Here is a gem I never thought of: Instead of telling a student that he or should should have done xyz instead of what they did, abc, ask questions. Why did you do abc? What were you hoping to accomplish? Did you think of alternatives to abc?
By serendipity, a book I finished post NITA makes the same point. Check out, "Seeing What Others Don't:The Remarkable Ways We Gain Insights" by Gary Klein, which discusses this method. He writes, "This kind of teaching is very hard. It takes more than knowing the right answers. It takes curiosity and compassion and the ability to decenter--to take someone else's perspective."
So, the next time a teaching moment comes up, ask, don't tell.