On my last night at South by Southwest, I sat next to my friend Cindy at dinner and she taught me some of the Mandarin she had been learning for her own upcoming trip to China. She wrote down a few key phrases she thought I might need, namely: xie xie (“thank you”), wo yao kafei (“I want coffee”) and bu yao (“I don’t want that”—or, in the words of the newly minted Darth Vader, “Do not want!”).

She reckoned the bu yao would be handy because, as an obvious foreigner in China, I would be an easy target for people trying to aggressively sell me knock-off Rolexes or fake Chanel bags. And sure enough, whenever Jeremy and I have walked down the pedestrianized shopping superhighway that is Nanjing Road or frequented any other high-tourist-traffic areas in Shanghai, we’ve been repeatedly intercepted by people waving flyers at us and asking if we want “WatchBagShopping?” or “TshirtDVD?”

My primary tactic for dealing with touts is to just ignore them and keep walking (which is pretty easy to do here seeing as I’m usually a good head taller than the person trying to get my attention). A raised hand and shake of the head can often do the trick as well. But for the most persistent hawkers—the ones who descend on you as soon as you stop to look at something or who follow you down the street even after you’ve said “no”—there is only one 100% foolproof tactic, and that is to say a firm and decisive “Bu yao!”

Weirdly, it seems to work like magic every time. Ignore them or shake your head and the hawkers might go away, but they might also stick with you. But say bu yao and they seem to disappear in a puff of smoke. Jeremy said it’s like being in a video game: as you walk down the street, the “bad guys” keep popping up in front of you left and right and you have to knock them down with your bu yaos so you can continue moving forward. When you get to the higher-level hawkers, you may need two well-aimed bu yaos to take them out, and for the boss level it might take three. But eventually it will have the intended effect.

Twice today I saw fellow tourists failing to shake off aggressive salespeople with diffident refusals, and both times I wanted to shout, “Say bu yao! Say bu yao!” I didn’t say it then, but I’m saying it now to the non-Mandarin-speaking world at large: if you learn no other words of Chinese before traveling to Shanghai, learn xie xie, and for god’s sake, learn bu yao. Oh, and learning xiaolongbao (“soup dumplings”) wouldn’t be bad either—but that’s another post for another time.