The airport-taxi swap
Someone offers you an official-looking taxi (or your "pre-booked" one) at the airport. Rate is fine, but they detour to a "government tourist office" (fake) or their friend's carpet shop. Only use prepaid taxi counters (official kiosks) or Ola/Uber.
The temple + shop guide
A friendly local at a temple offers to show you around "for free". Great tour, then a stop at their friend's shop — where you're expected to buy carpets/gems/handicrafts. Say no politely and leave; don't feel bad, this is a normal daily transaction for them.
The train-ticket "cancellation"
Someone at a station tells you your booking has been "cancelled" and hurries you to a "tourist ticket office" that's actually a travel agent's office. Ignore + go to the actual ticket counter. Your booking is fine.
The gem-import scheme
A shopkeeper offers you a great price on gems if you "just carry them back" to your country + resell for a profit. It's an elaborate confidence trick — the gems are worthless glass. Never do this. Ever.
General rule
Anyone who approaches you unsolicited with an "opportunity" is running a script. Anyone who follows you three shops after you said no is desperate. Anyone who says "I'm not a guide" then guides you for 30 minutes wants a tip. All normal; just say no clearly.