There are common scams that occur in many places that the traveller should be aware of.
These are designed to get your money or business from you under false pretenses.
These scams are based upon the idea of offering you help or advice that is actually deceptive, trusting that you will rely on the scammer's "local knowledge".
They usually involve giving advice that results in you paying for something that you otherwise wouldn't or going somewhere you don't want to go.
At the same time, if you do get stung, don't be too hard on yourself: you were dealing with people who knew the location a lot better than you and with people who were out to deceive you.
In some cases, you were dealing with hardened criminals.
If you think what happened to you was illegal and the police are trustworthy, report it, otherwise, just chalk it up to experience.
Note that if you wish to make a theft-related claim against an insurance policy, you will generally need to make a police report within 24 hours and keep a copy for your insurance company.
While you shouldn't become a hard-nosed nasty person, you should receive unsolicited offers of help with polite caution, and, when you are reasonably certain that you're being scammed, there's no need to be polite in fending it off: feel free to walk away or speak firmly at the person.Yelling for help could be necessary, but it will often just attract more (unwanted) attention.They fall into three categories: overcharging you, deceiving you or coercing you into paying for a service you don't want, and outright theft.Prevention is based on knowledge: researching your destination will both alert you in advance to scams in the area and let you know what the usual prices and truly good sights are so you will be less reliant on the approaches of helpful individuals when you're vulnerable.
Some scams in which a helpful local offers to cut you a good deal can be outright fraudulent such as convincing you to buy fake gems for example but many simply get you to pay for something that you wouldn't pay for if you knew the area better.
One of the biggest traps of these kinds of scams is the desire to be polite to people who are polite and friendly to you; and the scammers know this.