Tipping in Brazil is typically not expected nor given. Usually, Brazilians only consider giving an extra if there was some special, nonstandard service. However, if you are a foreign guest with a good exchange rate and can easily afford to be generous, service people will be grateful.
At almost all restaurants and bars, a standard "serviço" service fee of 10% is included as a line item at the end of the "conta" or bill. This fee is not compulsory, even though it may seem so. However, most people do pay it unless there's a good reason not to (e.g. a very bad service or an absence of service - at places where you were not waited on). Although optional, some waiters may complain or may react negatively if you decide not to pay the 10% service fee.
Tipping in Bars and Restaurants
The term bar in Brazil is not used a synonym for a nightclub or for a indoor property with music. It's rather used to refer to restaurants where people usually have appetizers and drinks, and which are usually open to the public, with no bouncers or whatsoever. In other words, a bar is a type of casual restaurant. At bars, the bartenders do not usually handle cash. In a bar or a restaurant, you ask the bartender for your bill, and he brings a total (usually with full details). You decide how you'll pay and then give the money, check or card. As most cards in Brazil are chip cards, the waiter or bartender will bring a card reader machine and will swipe the card in the presence of the client.
Tipping in Taxis
Make sure to understand the differences between a regular cab and a radio taxi. Radio taxis are available at airports in major Brazilian cities and charge set prices which vary depending on the destination. Therefore, taximeters are not used by radio taxi drivers. Regular cabs are those which circulate around the city using taximeters. They tend to be a second option at airports as well. In Rio de Janeiro, radio taxis are booked inside the terminal, whereas regular cabs wait outside the arrivals area, lined up, waiting for clients to come. In either case, it's not usual to tip a cab diver.
Common taxis (yellow in Rio de Janeiro and white in São Paulo) run on a taxi meter. Typically, if the total for the trip comes to say R$12.20 (i.e. a bit above R$12.00), people pay the amount round to the next whole number (in this case R$13.00) so that no one has to deal with coins. No other tip is required or expected. To/From the airport, a taxi may apply a R$3 per case charge on top of the fare. This happens occasionally and, supposedly, they have a right to ask for it. However, if they apply this charge, they should definitely transfer your luggage out of the car for you. There are also special or radio taxis. These typically quote prices for a trip and do not use a taxi meter. A tip should not be given in this case as you are already paying a higher price for these taxis.
Tipping in hotels
For most hotels, tip the bell hop if they transfer all of your luggage to/from the room. In this case a small tip (R$5 to R$10) is appreciated. The chamber maid should be tipped (about R$5+ per day) for good service, as she is integral to the enjoyment of your trip.
Tipping to guides
Organized tours (especially boat trips) also typically make a request of a tip by passing the hat at the end of the tour. It is up to the individual if and how much they wish to give to the crew.