After you arrive
1. Although cards are widely accepted in Brazil, get some cash and always carry it with you in case you need to pay for parking or flanelinhas (people who watch cars on the street) or some merchandise from informal vendors (most of them accept cards). Exchange part of your national currency or withdraw at an ATM (almost all shopping malls have an ATM).
2. First and second generation Brazilian real banknotes are still accepted, but if you go to an exchange office, prefer the second generation (second and third photo). See the Reais coins in the last photo.
Go check out my guide for the best free things to do as well as itineraries and travel tips to make your trip unforgettable.