Tea house Scam
You are happily wandering around somewhere like Wangfujin or Tiananmen and a friendly English student starts chatting to you. He or she will speak excellent English. They will be friendly and show you around, maybe helps you buy a few gifts, and subsequently suggests you go for a cup of tea at a nice tea house he / she knows. The tea house will be very nice, you will have some very nice tea, but you will feel slightly disturbed by the fact that they served tea without letting you see a menu, or that the menu has no prices on. You will assume this is how you do things in China.
When the bill comes it will be ridiculous. Well for tea anyway, 800-4000RMB is not unheard of. Big beefy guys will attempt to pressure you into paying. Don't as they won't have a leg to stand on if you call the cops, worst you can do is be deported, worst that can happen to these people is they get shut down for corruption. What happens now varies - some scream and shout, some yell for the cops meekly, even if it requires the use of foreign currency or a credit card because they haven't got enough RMB on them.
1) Art galleries. 'Art students' strike up a conversation and invite you to their gallery. You'll see at best second rate art at top-rate prices, and will be lucky to avoid a high-pressure sales pitch. Spend your time at a real gallery. Real galleries, for reference, do not send English students out onto the streets pretending to be art students.
2) Bars. Seems to be more common in Shanghai, and uses pretty girls in too much make-up rather than innocent looking 'English students' in tracksuits. This is clearly because Shanghai attracts a lower-class of tourist, but that's beside the point.
In any case, you'll be in danger of paying a lot more for something than you should do, and at the very least you're going to waste your time.
Heh TCG in Mongolia got into a fake taxi once, the meter started flying the moment I got on board (granted Mongolian money is piss weak) but once he got to the hostel I got out and walked away.
Meeting people makes your travels, so thus you may well get some legitimate people and may thus miss out on this. I remember the time when I really did win £50, but kept thinking yeah right what a scam and ignored it for MONTHS. Or the time when a bank branch was giving was £5 notes to its first 100 customers everybody thought it was a scam.
The way to disarm this is to say I prefer coffee, and the cup cakes in Starbucks (or some other pay first place in Beijing of which there are many). If it is a scam they'll walk away, if it isn't they'll say ok and you can enjoy hob nobbing with the locals.