As long as there are tourists, there will be scammers. Unfortunately that’s just the way it is. I don’t go into all the different types I’ve encountered because there are so many and I’m sure there are countless more out there.
I will say this as a basic rule of caution. If someone asks you for money, just walk away. Let them ask all they want but don’t reach for your wallet. In some countries, I even carry an old decoy wallet. I figure if they’ll leave me alone as soon as they get it so if they get a raggedy old wallet I was going to throw out anyways and it buys me time to get out of there, then that’s a win.
Also, if anyone approaches you to sell you something, you should immediately think scam. If I want something whether it’s food or a souvenir, I go the shop. I don’t wait for someone to approach me. Think about it like this. If you were in you local parking lot on your way into a store and someone offered to sell you something in the lot, would you accept or keep walking? That’s how I feel about people approaching me when they’re selling something.
Expect to be shortchanged. When dealing with cash, it might be best to write out the amount in a notebook so it gives you time to really think about what change you should be getting. If possible, I try to pay as close to the amount as possible. I’m not going to care if I get short changed by a few cents so I try to give as close to exact change as possible.
These are basic rules but here’s the thing. You won’t be able to catch every scam. And the only way you’ll know you were scammed is after the fact when it’s too late. Although I don’t walk around blindly trusting people, I don’t let the loss of a few dollars deter from my experience either. No one likes to be taken but it happens. What I try to do is just minimize my losses and move on. I’m on vacation and ultimately I don’t want a bad experience to detract from my overall trip.