These are designed to get your money or business from you under false pretenses.They fall into three categories: overcharging you, deceiving you or coercing you into paying for a service you don't want, and outright theft.
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.
Your driver or guide will tell you that the place you're heading to is closed, no good or too expensive and that he knows somewhere better.
While this may be true, it's likely that the 'better' place is giving him a commission for referrals, and his commission is just going to increase your room rate.
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.
Several bits of common sense may help you stay out of trouble without your needing to know exactly what scams are practiced in what areas: Research into your destination, its general layout, and the usual price ranges are helpful in avoiding many scams.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.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.Pretending they don't exist, which entails not making eye contact, not walking faster, not saying 'hello' or 'no', will often humiliate them or tire them out without frustration on your part.Do not respond if they call you racist to attract your attention.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.