Get the proper shots for Yellow Fever. Brazil requires all visitors to the country to be vaccinated against Yellow Fever.
Just have your hotel clerk call a taxi for you. Genuine cabs have red or maroon license plates, but this is no guarantee.
The favelas might look nice, but they can be very dangerous for tourists.
Brazil is a hot place, so be sure to stay hydrated by drinking at least two litres of mineral water or coconut water per day.
Don't stay too long in the sun, and wear sun lotion with the highest SPF you can find.
There are disease-carrying mosquitoes in some parts of Brazil, so be sure to apply insect repellent before you get bitten.
Never carry huge amounts of cash with you on the street. Take only what you need for the day, and keep it safe in your money belt.
Do yourself a favour and take only a bear minimum of possessions out and about with you.
Photocopy your passport and visa, and carry these copies around with you rather than the originals and use these, rather than the originals as ID when you're in Brazil. The last thing you want to be doing is trying to get replacement papers if they are lost or stolen on holiday.
Put your wallet in your front pocket, or better still, an under-clothes money belt in order to make it harder for people to steal it.
Don't wear expensive looking jewellery and watches, as this can be a magnet for muggers. Just get yourself a cheap watch and wear that while you're away.
Always avoid very congested places, as these are popular hunting grounds for pickpockets.
Never walk alone at night on empty streets. Even if this means your journey time is elongated, it's better to be safe than sorry.
Be sure to hire a real taxi, especially in Sao Paulo and Rio de Janeiro. Some unlicensed drivers have been known to portray themselves as real taxis, when they are anything but.