We will be coming in to Florence for the day by hire car from the countryside where we're staying (near Siena). Where can I park?
The main train station, Santa Maria Novella, has plenty of underground parking but it can be quite expensive to leave your car here for the day (the costs are currently around 2 euro for the first two hours then 3 euro per hour after that - an 8 hour park can cost you upwards of 20 euro). Other options are to find street parking outside of the traffic limited zone (ZTL) or to use a garage (also very expensive).
In general, street parking in Florence is difficult to find and you can easily risk accidentally driving into the ZTL areas. But if you are determined, here are a few guidelines for street parking: first of all, look for a sign with a white 'P' on a blue background, or the word 'Parcheggio' which means parking. Blue lines marking bays on the street indicate pay parking (avoid the white ones, they are for residents only, and yellow ones for handicapped parking). Once parked, you will need to buy a ticket from a machine, then display it clearly inside the car. Florence's parking inspectors are notorious for their sharp eyes and quick pens!
If you are leaving your car overnight, be aware that most streets and piazzas have a certain time (between 12am and 6am) of the week when they get cleaned, and you risk your car being towed away – pay attention around you and use common sense. If you see a large number of parking spaces, you must ask yourself why! Florence has very, very little parking, so you should be lucky to see even one! Often, parking in the outskirts of Florence is a good way to avoid these hazards (see the question "parking outside Florence").
Look at www.slowtrav.com/italy/driving/parking.htm for good photos of common Italian road signs and further explanations of rules