The currency is the Real - R$.
Most credit cards are widely accepted, but there can sometimes be technical issues with cards issued outside of Brazil. Carry a little cash wherever you go just in case.
ATMs are widely accessible, but sometimes they only work with cards issued in Brazil. Ask at hotel reception for the nearest "international" ATMs.
Parents or legal guardians traveling with children under the age of 18 must present the child's birth certificate and an identity card with photo at the check-in at hotels. If only one parent is traveling with the child, she/he must also present a notarized letter authorizing the trip signed by the other parent. If traveling with children, consult the Brazilian consulate before travel.
Sao Paolo has an extensive and busy Metro network. Rio, Recife Belo Horizonte and the capital Brasilia do as well but not as developed. There is no interconnection by train between main cities, and airports are NOT linked to the Metro lines. Metro lines are reliable and safe, the few overground lines vary in quality and are not recommended.
Brazil is huge. The roads in Sao Paolo, Rio, in the south of the country and around the main capital cities in the north-east are okay to drive, but keep in mind that the driving standards in Brazil are very poor. Avoid exploring smaller village in the countryside or the Amazon. Highways outside the Sao Paulo-Rio region are not recommended either.
TAM, GOL and Avianca have flights to most domestic destinations as well as direct flights to South America, Europe and the US. Passaredo and Azul are domestic only and have flights to the main Brazilian airports.