I expected the Brazilian culture to be different from the American culture I grew up in, but I was not really ready for it all when I arrived. No amount of preparation can save you from the initial awkwardness of experiencing new customs, but here are a few warnings about the major culture shocks in Brazil.
Every time people say hello in Brazil they will try and touch you. Girls kiss your cheek and give you a hug. Sometimes they only kiss one cheek and sometimes both, but it is usually just the left one. Boys always give you a high five or a fist bump or something that resembles a secret handshake which neither of you knows. The whole point is to establish contact, but more often then not I have botched the hug/kiss/handshake and left both parties laughing. Although it can be frustrating, Brazilians are quick to forgive and forget, and will usually try and make a joke to help you feel better about your mistake.
I have been on time to a social function where the host was not even at the venue yet. In Brazil, especially in the North East region, people are always late. It is customary to arrive an hour or two late in São Luís, but the degree of tardiness varies from region to region. When scheduling a party or event the host "marks" the time, but it is assumed that they will only start getting ready at that time. You should also start getting ready then and everyone will meet up after a fashion. There is never any rush to be on time except for school or work-related events and at weddings.
Usually, the whole group will disperse at the same time. Everyone says goodbye and repeats the hug/kiss/handshake process then continues talking for about another 30 minutes. After that time has elapsed you repeat the whole thing and then go your separate ways. It is rude to leave too soon.
Everyone has a birthday party regardless of their age. Brazilians love to party and birthdays always provide a reason. For young people, the parties are usually surprises. The birthday song has more than one verse and is sung almost competitively among the guests. The first piece of cake is given to the most important guest by the birthday boy/girl and they are supposed to give an acceptance speech. I am impressed by how festive Brazilians can be for a birthday.
I am still learning new things about Brazilian culture all the time. Whenever I make a mistake like showing up on time or forgetting to kiss a stranger's cheek the locals always make light of my follies. Brazilian culture is very open and welcoming, so although you may feel like a foreigner, you will never feel left out.