Robert Cialdini explains how to make favors stick: praise the recipient, make the help visible, and say "If the situation were ever reversed, I know you'd do the same for me." This frames the favor as a future obligation and triggers reciprocity when roles flip.
know that if the situation were ever reversed, you'd do the same for me. I give them a compliment to live, uh, live up to, a reputation to live up to. And put the— don't dismiss what I did for them. I don't demean it. I don't ignore it. I put it on the map, leave it on the map and say, okay, you're the kind of person who, um, who lives up to his, uh, or her, uh, obligations. And, and sure enough, everything changed. Wow. Wow. I think that's one single sentence anybody could use. Anybody. If this situation were ever to be reversed, I know you'd do the same for me. That's the future.
