When in a restaurant, the tip is often included in the bill, but when not, tipping rules are generally the same as in the U.S. - 10% for bad service, 15% for good and 15% for excellent. A tip is called a 'gorjeta' in Brazil.
In Brazil it is considered rude to eat a sandwich with one's bare hands, people hold their sandwiches with a napkin, or as is often the case, if the sandwich comes in a small paper bag/wrapper, they will hold it with the bag.
It is also considered rude to eat pizza using one's hands, typically pizza is eaten using a knife and fork.
After a meal, if you use a toothpick, it is polite to use your free hand to cover your mouth - it is considered rude to allow your tooth-picking to be seen.
Dating rules are different as well in Brazil: there isn't the same approach to casual dating as in the U.S. If two people are interested in each other, they will typically go out in a group with friends until the two know each other well, and will only go out alone if a serious relationship is being considered.
When two young people become engaged, the young man will wear a silver ring on his ring finger to indicate that he is engaged. The young woman will wear an engagement ring as is typical in most countries.
Family ties in Brazil are very strong, and typically families will live in close proximity to their extended family, often in the same household. A young man or woman will often live with his/her parents until he/she is ready to be married.
Brazilians are by nature a very warm and friendly people. Friends traditionally greet one another in one of two ways: the 'beijinho' (little kiss), or the 'abraco' (hug), and a greeting such as 'Bom dia' ('Good morning or day'). Other greetings used include 'Como vai?' ('How are you?')or if meeting someone for the first time 'Prazer em conhece-lo' ('Its a pleasure to meet you'). Appropriate responses to 'Bom dia' would be to answer the same thing back, and to 'Como vai?' to answer 'Tudo bem , e voce?' ('All is well, and you?').
When two men who are friends meet one another, they will typically shake each other's hand while at the same time patting each other on the back in a manly fashion - the abraco.
When two women greet one another, they will use the beijinho. This typically consists of brushing the cheek on either side once for married women, and adding a third for unmarried girls. The third beijinho is to wish the single girl good luck in finding a husband. If you are unsure of the marital status of the woman you are meeting/greeting, you may forgo the beijinho and just use a standard hand shake.
This same beijinho rule applies to when a man and a woman meet each other, and in my experience, I have noted that this kind of greeting is usually used by the younger crowd, but is used by all when they know each other well. The beijinho is often used when a young man and woman are meeting for the first time as well.
When parting company, a typical thing to say would be 'Ate logo' ('See you soon'), or 'Tchau' (pronounced 'chow', which means 'good-bye' or 'bye').
In Brazil, personal space is less of a concern than in the U.S., and in converastion it is not unsusual for two people to be much closer to each other space-wise than would typically be seen in other countries. If someone is speaking to you and they seem uncomfortably close, it is just a cultural difference and shouldn't be deemed offensive.