As a number of posters have said, just use common sense. Use taxis at night. Try the restaurants Marius in Leme for seafood, or Porcão in Flamengo or Ipanema for great Brazilian steak. These are don't miss. If you are there on a weekend, go to the Hippy Fair (Feria de Hippi) in Ipanema. Don't wear jewelry, and carry only as much cash as you need, and you will be fine. The vast majority of Brasilians are wonderful, and have a great outlook on life. Just don't expect them to be on time.