The interview is usually very friendly and candidates are made to feel at home. Interviews are usually one-to-one. If the job is not specialised, there will be only one interview, but for a specialised occupation that requires experience, shortlisting is the order of the day, followed by one or two additional interviews. You may be expected to make a presentation in this case.
Keep to the point of the discussion/questions and do not invent ski lls that you do not possess. Show that you are willing to learn. Eye contact is important, as is body language.
You can ask questions, although these are best kept to a minimum and must be relevant. Asking for a job description or about working conditions might be advisable. If there is a second interview, it is better not to discuss pay at this stage.
The more you know about the company, the better. This shows that you have taken an interest in getting to know the company, its past performance and future plans. Your enthusiasm may even enhance your chance of being selected. The most common question an applicant is expected to be able to answer is about the core function of the company. Another is whether the company is a subsidiary of another company or whether it exports its products and to what countries, if this is the case.
One tricky question an employer might ask is what pay you expect. There are various ways of answering this, especially if you have done your research and have sufficient experience.