Brazilians are much more liberal with body touching and personal space than Americans. This is generally a very cool thing. You will often see even younger boys holding hands as a sign of friendship. Women do the two-kiss greeting. But beware. Don't automatically go in for the air-kiss on each cheek. Only for informal situations or with people you already know. Estrangeiros are granted plenty of leeway on this, but if it's a cordial situation a handshake is the default. Also, men (almost) never cheek-kiss other men! don't be surprised by a warm embrace between men that are good friends. Remember: it's just one or both cheeks, never three pecks as some other countries.
Especially in residential buildings. Complete strangers will commonly say bom dia and, tchau when entering or exiting. Brazilians feel uncomfortable with the silence that we consider normal.
It's very rare that a storekeeper will do the standard change-count when paying for something. If you want to verify the change was correct just do a quick check while you're still in their presence. Brazilians are very honest with making change.
Brazilians will order an item or food by saying Give me the plate of the day, but it's not considered polite unless you add the por favor to the end. Like this: Me dá o prato do dia, por favor.
Unless it's a very casual engagement you must always call to confirm an appointment or date just before it's scheduled. Even business meetings. You can use facebook, whatsapp or email to confirm, but unless you get an answer - it's not confirmed. Really. If its something you care about but you don't confirm, you may be disappointed.
It's of course considered rude to leave a party without saying good-bye. But it's also important to excuse yourself when leaving the dinner table - even if you don't know the people sitting with you. If you are sharing a table with a stranger and you get up to get a salad you say com licença.
This seemed really weird to me at first. Now it doesn't! Unless it's a cordial or business situation, the normal end to a conversation is um beijo (to a woman) or um abraço (to a man or a woman). It does not imply intimacy, it's just the norm so do it!
The standards of etiquette in Brazil are better, more natural, and more fun. In my humble opinion. Except for the lateness.