Avoid taking cabs in Prague because it is almost impossible to find a honest driver. They almost always overcharge tourists. If you must take a taxi (i.e. you are hopelessly lost or you missed the last train), make sure to agree on a price before you go anywhere, if they don’t have a meter. Otherwise you will get taken.
The taxi drivers can be very aggressive, some of them got gun in their cars and electric chairs at the passengers seat in case people do not want to pay. If you have to take a taxi make sure you agree on a price before you start to drive. The taxis should have the taximeter on.
There has been many reports that when passengers has been arguing about price some taxi drivers use inappropriate aggressive behaviour. Agree on price before you get in to taxi.
Reasons for this were that there were too many licenses issued and no regulation of their activities. However the final straw appears to have broken the camel’s back. One passenger objected to being charger 8,000 CZK (250 USD) for a ride of about 3 kilometres and the City Hall had to step in with a solution. The deregulation of rates from October 15, 1996 had been cancelled and instead the strict guidelines were introduced. Unfortunately it didn’t help much.