Taxis in Florence are white with a sign on the roof. You’ll see them easily enough; you just won’t be able to flag one down on the street. Instead either call one, or make your way to a taxi stand at the airport, main stations or squares.
They can be expensive, but with access to lots of streets prohibited to other traffic, can get you to where you want to go quickly.
The meter displays what you have to pay, though there may be some extra charges, for large suitcases for example.
Being a woman helps your finances in Florence. Travel alone between 21.00 and 02.00 you’ll get a 10% discount. You’ll have to ask for it though. And no guys, don’t try and fool the driver, they’re seen that trick a million times.
Another way to save money is by using Taxi Multiplo. Three or more people going to the same area can share a ride from an official taxi stand.