Assuming that you have sent the company your CV and they have called you in for an interview the best advice I can give for successfully passing is as follows:
1. Do your homework, find out as much about the company and the job you are applying for as possible. Use different sources, internet, friends, speak with other employees in the company and don't forget the receptionist. This way when you are asked questions by your interviewer you can demonstrate that you are interested in the company. Don't be afraid to ask interesting questions about the company during the interview (not about the job).
2. You should have at least a passable level of fluency in the Portuguese language. It is essential that you can communicate effectively with the interviewer and eventually with your co-workers should you be chosen for the position.
3. How you dress for the interview obviously depends a lot on the position you are applying for. However, the rule of thumb is do not dress in casual attire. For men a dress shirt and tie, dress pants or for a woman, blouse and skirt or dress pants and perhaps a colored kerchief tied around the neck are never out of place. For high-level positions a business suit is recommended for both men and women. Brazilians seem to favor the colors black and dark blue as far as suits go. White shirts or blouses, the only real variation in colors is their ties.
4. Behavior during the interview. Shaking hands is customary, although Brazilians are a "huggy" society do not try to hug anyone in the workplace until you have been employed there for a while, it is generally frowned upon. No matter how nerveous you are about the interview your handshake should be firm and confident, but not too strong.
Eye contact with the interviewer is essential and your body language is also important. Bad posture, even crossed legs for men especially might be seen as a lack of interest. Proximity is also a rather tricky issue. You must be close enough to show that you are engaged in the conversation, but not so much so as to invade the interviewer's "personal comfort zone".
Never chew gum during the interview, it is considered highly rude to chew gum in the workplace in Brazil. Do not fiddle with pens, pencils, your eyeglasses, hair, etc. during the interview. Any sign of nerveousness will scuttle the whole deal.
5. Answer questions honestly, remember that here in Brazil an interviewer is likely to ask (and may do so) certain questions that would not be permitted during an interview in your home country such as marital status, age, number of children, sickness record,and many other personal questions.
6. Remember that the interview process here in Brazil generally has several different steps, so don't be surprised if there is a second or even third interview - it is common here. You will also likely be subjected to a psychometric test during the process. Brazilian firms are really big on that (don't know why). Your references will be checked out thoroughly, either before you get called for the interview or somewhere during the process before a firm job offer is made.
7. Be prepared for the interviewer to ask the standard question... "Why are you leaving your present job?" Try to give an original answer, the old "the job doesn't offer me challenge" or "there's not much potential for growth" don't cut it anymore.
Stay calm, be yourself and good luck!