1. In my opinion all these qualities are importants but maybe the most important is work experience and the second is personality. Your work experience proves that you are able to do some specific tasks and your personality gives information about your habilities to make up in a team or company.
2. In general interviews are a difficult but necessary step before join in a company.
3. I think the most important thing is to prepare the interview. You have to search information about the company and try to analyze your strenghs and weaknesses.