The answer to this will depend on many factors, things like, will you be interviewed by an Angolan or expat from another country. But the most basic principles stay the same for all Interviews and you can research this on google, all the general do's and dont's. But for Angola I would suggest the following.
If you know Portugese you have won 70% of the battle. Dress very smartly and show respect all the times when dealing with anyone inside the company and during the Interview, respect in Angola will take you quite far.
Another thing if you are Interviewed by an Angolan, compliment Angola for the development which they achieved in a short time from 2002 until now. They love compliments.
If you don't know Portuguese just say so, but also say that you are very interested to learn the language and whether they know of any classes or schools, this will help as well.
Be yourself, relax, have a positive outlook and be self confident and don't be shy if you don't know something.
Hope this helps.
