While tipping is not customary in Florence, if you experienced top-notch service, a tip of 5%-10% of the bill would be nice. You do not need to tip taxi drivers unless they help carry your luggage.  For hotels, it is normal to give your porter about €2 when bringing your suitcases to your room. A normal rate of 5%-10% is the normal rate given to tour guides as an appreciative gesture although it is not obligatory.