Get a yes to a vague favor, then reveal the catch — most people don't back out
Cialdini and colleagues asked students to join a 7 a.m. study, either naming the time upfront or only after they'd already agreed to take part. Revealing the costly detail after commitment roughly doubled the agreement rate, and almost none of those students backed out once they learned the catch. The trick, low-balling, works because a commitment feels binding even after the terms quietly get worse.