If you arrive a few days in advance, you could catch performances by some of Brazil's top bands specially called for the event. Araketu peformed when I was there .. it was a blast ... and it was free !
This is clearly the thing to do during the three days of the carnival. Go early to find yourself a good spot in the stadium, called the Bumbódromo. It can seat about 30 thousand people, clearly divided into the Caprichoso side and the Garintido side. Please do not wear red and sit on the blue side of the stadium or vice versa. Every once in a while you can see some dude (wearing the wrong colored shirt) being lifted and carried out of that part of the stadium. There is no violence and the venue is very safe. Its a treat to watch the enthusiasm and passion of thousands as they support their side. Even before the carnival starts, the two sides tease each other with gestures and shouts.
The stadium also has a portion of the seating dedicated to rich/important guests ... you can sit in air conditioned comfort and watch the carnival from behind glass walls .. much like watching football from the VIP section.
The carnival itself was a sight to behold. We were supporting the Garantido on the first day .... all the Garantido fans were given candles that we lit up during the carnival. There were guys on the ground whose dance steps we had to follow ... can you imagine 15 thousand people dancing the same way as the Garantido floats make their entrance ? the caprichosos prefered to maintain stoic silence during this time, as expected :)
Banana boat ride to a remote village in the rain forest: 30 dollars. 3 shots of cachaca before the event: 5 dollars. Making mexican waves with candles in your hand while singing folk songs in portuguese as the floats come by: priceless !
Dress Code: nothing