I have posted several places about this topic, but basically I wanted to be very explicit and put a lot of things all in one place.
I have gotten along fine for months here using primarily credit cards and an atm/debit card to get cash. To use a debit card to get cash, you need to find an international ATM, which is usually indicated by a raft of stickers that the other machines don’t have, featuring things like VISA, PULSE (or is it PLUS?), American Express, etc. In Porto Alegre I usually use Banco de 24 Horas machines. In Rio I have used machines from Banco do Brasil, Bradesco, HSBC, Citibank, and more. Many will have the option of instructions in English. You do have to watch for scams. Criminals have invented a machine they put on top of ATMs to steal debit card information and I know Americans who have been hit (in Rio).
Sometimes the ATM machines will tell you the exchange rate before finishing the transaction, sometimes not. There is always some kind of additional international fee and/or currency conversion fee, usually 2-3 percent. As in the U.S., there is a daily limit.
The most reliable places for me to find international ATMs has been in malls. Sometimes supermarkets (which are sometimes in malls). Just walking into banks on the street has been very uncertain, without much luck most places, although in tourist areas of Rio you can find them there.
You can also use debit cards, and often credit cards, at the larger supermarkets. They will usually ask which one you have (debito or credito?) and may want the last four numbers of the card. For debit cards you will also need to key in your PIN.
Credit card companies are suspicous these days. I have had cards suspended when I’ve used them nearly daily on a two-week vacation in Brazil. You can imagine what can happen when you live here. I have a couple of cards that I called in about, telling the company that I would be living here this year and that I would be using the cards to make charges. So far so good. I haven’t had either card suspended. I have also avoided using them for U.S. charges. So I have my U.S. cards and my Brazil cards.
I haven’t done this, but I imagine it would be a good idea to photocopy your cards and keep phone numbers to call in case of loss or theft, although I do essentially everything online. I pay my credit cards online via transfer from my U.S. checking account, and know what I am using and carrying.
I have gotten by without checks. I give my friends cash or send them money via paypal. Paypal works in Brazil. Paypal does have a 3 percent fee. Paypal also sniffs for suspicious transactions (e.g., an American sending money to a Brazilian) and can suspend accounts and/or transactions, requiring a few days to process investigations (generally asking for explanations, new passwords, etc.).
The name of the game is having multiple ways to pay for something and back-ups.
Also, when I am in Rio the wallet is always in a front pocket and I generally keep some loose cash in a different pocket. Safer that way paying for cabs and things without needing the wallet.
Don’t tip in general. It will be made clear when a tip is customary, and it is not most places. I will usually tip the taxi driver, however, when I am taking home groceries or something like that and he helps with the loading and unloading in the trunk.
Prices are rounded to the nearest 0.05 reais, or five centavos, and sometimes those will get ignored. Still, you will see prices like R$19.99 and R$29.99.
When buying more expensive items and paying with a credit card you will be asked if you want to pay in installments (the number of payments depends on the price). Sometimes you get a break paying all at once, but often it is the same price.