When arriving in a new city, from my hotel room (which I always chose in the middle of the hotel area of the city), I walk to a nearby 5 star hotel. They always have a line of taxi cabs waiting in their drive way. They only allow good taxi drivers to pick up their guests. I don't know what the procedure is for a 5 star hotel when it comes to chosing their taxi cabs, but I am sure they use a registration system and they vet the drivers very well because the hotel does not want do lose guests/get bad publicity because of a bad taxi driver. So, I walk to the line of taxi cabs and I get into the first one as if I were a guest of the hotel (worst scenario is that I have to give a tip to the bell boy at the door of the hotel). If I like the driver, I will get his phone number and will ask him to pick me up on other days. When I go to more than one destination in one day, it is usually better to reserve the taxi driver for the whole day: It's a little more expensive, but you have a safe taxi cab waiting for you after each meeting, ready to take you to the next destination/your hotel.