Most people use taxis at some time or another. Here is advice for travelling that is relevant even in your home town, especially if you are on the way to an airport, bus or train station.
Most taxi drivers are honest people just trying to earn a living for their families. However, I have lived in a city where some taxi drivers are involved in organised crime.
When a taxi driver asks you details about yourself, your home, your destination or the purpose of your journey, he is probably just being friendly. However, if you truthfully answer his or her questions, you may be giving information that an accomplice could use to burgle your home. The driver may know whether your home is empty and how long you are expected to be away.
Even If you do not deliberately give information to your driver, if you frequently use the same taxi company, drivers may get to know your habits. For that reason, consider using a variety of taxi companies if you frequently travel in taxis to or from your home.
If a driver asks questions that could compromise the security of your home, do not hurt his feelings by simply refusing to answer. Rather, give obscure replies or tell "white lies". The driver is probably, after all, just trying to be amiable but WHY TAKE THE CHANCE?
As I mentioned, most taxi drivers are honest. However, another thing to watch out for is the monetary change you get back when you pay the driver. Every fake pound coin that I ever received was from a taxi driver. For that reason, I always try to give the driver the precise amount of cash so that he doesn't have to make change.
Even then I have to be careful. On one occasion, I gave a driver perfectly good pound coins but he told me that one was fake and he showed me a coin that was a completely different colour to any that had been in my possession. There was little point in making a fuss with a rough looking customer, so I had to take the coin and give him another. Since then, I have always made a show of carefully examining the coins before passing them to the driver, so that he realises that I would see the difference if he swapped one for a fake.
Another scam involves offering to return supermarket trolleys for you. Nowadays, getting a supermarket trolley involves depositing a pound in a chain. On two occasions, taxi drivers told me that they were unable to get my deposit back. That has never, ever, happened when I return the trolley myself.