Tipping or not tipping, that is the question. Wherever you go in the world that is a first world issue.
Here in Brasilia most of the restaurants and bars will have a 10% tip added automatically to the bill; some, for example the Outback Steakhouse, will ask you if you want to add a tip to the bill and how high. Adding to the bill is generous and appreciated; however, it is not expected.
It is not obligatory to tip in hotels or for other services. But be generous to a point (please do not overdo it as some Brazilians will think that every gringo is a walking bank). Just keep in mind the minimum wage in Brazil is around 1100 reais a month, so a little money helps a lot, especially the poorer people.
If you park your car in one of the many public car parks you will find that it is most likely a “territory” of a group of people that consider the place their place of work. They will help you to park and unpark, “guard” your car and sometimes even wash it for you for an additional fee (R$35-50). You do not have to give them anything, but a 2 real note will not go astray and will help someone to support his family.