Hello VW Vagabonds, and welcome to the boards!
Always use the official taxi stand outside the airport, train station and ignore any offers for "deals" before you get to the curb. They will generally be just out front or there will signs to the side entrance where the line of taxis will be waiting. Taxis from the taxi rank will be reputable.
If you're staying somewhere I would simply ask them to call you a taxi when you are ready. If you want a back up plan the taxi rank will have taxi contact numbers posted and you could grab a picture of the sign, the side of the cab and/or ask the taxi driver for company contact information. There will be additional charge for them being called to your location but this is all part of the agreed fare charges.
If you want to pay by credit card its not a bad idea to confirm that the terminal is working before you set off.
"Pago con carde di credito?"
If you want to be extra careful you can tell the driver you want a receipt which will have his driver number on it, but this is really overkill.
"Posso avere una ricevuta?" re-CHEE-ta-vuta
But the chances are your driver will speak English and if not a lot certainly enough to discuss payments and receipts.
It's not a bad idea to have the address of the place you're going handy to give to the driver unless your Italian is pretty good.
Follow the rules about stands and calling and you shouldn't have any problems. I haven't had an issue with questionable taxi behavior since I had to pay in lire.
Have a great trip,
=Tod
