ATMs are widespread in Italy. Major credit cards are widely accepted, but some smaller shops, trattorias and hotels might not take them.
Italians are not big tippers. Use the following as a rough guide:
Taxis Optional, but most people round up to the nearest euro.
Hotels Tip porters about €5 at high-end hotels.
Restaurants Service (servizio) is generally included in restaurants – if it's not, a euro or two is fine in pizzerias, 10% in restaurants.
Bars Optional, though many Italians leave small change on the bar when ordering coffee (usually €0.10 per coffee). If drinks are brought to your table, a small tip is generally appreciated.