Multibanco ATMs are widespread throughout the city; look for the MB logo. International credit cards – referred to as Visa, even when they are MasterCard and others! – can be problematic. Smaller family-run shops, restaurants and guesthouses will only accept Portuguese-issued debit cards as far as plastic goes.
Nova Câmbios The best bet for changing cash or travellers cheques is a private exchange bureau like this one.
Restaurants In touristy areas, 10% is perfectly fine (though it's never expected; few Portuguese ever leave more than a round up to the nearest euro, and only with cash transactions).
Bars/Snack Bars Not expected unless table service is provided, then no more than the loose change.
Taxis Not expected, but it's polite to round up to the nearest euro.
Hotels One euro per bag is standard; gratuity for cleaning staff is at your discretion.