1. Important qualities
If you want to impress an interviewer in a job interview, I think that is important a good appearance because is the first impression. Good appearance is the first that an interviewer sees when you arrive at job interview and I think is important to take care of it.
On the other hand, to have good qualifications is an important part of the interview but I think is not the most important. What makes a candidate good for a job is the work experience cause it's all the knowledge that the candidate has.
2. Job interviews
I have to say that I haven't done a job interview for a long time. I have been in the same company for 15 years. I work as a developer engineering and the interviews are very hard cause the first part of the interview is about knowledge, studies, qualifications, experience, etc… but the second part is the hardest part and it’s consists in an exam to prove the complete knowledge about different programming languages and different management tools. These kinds of interviews are very heavy.
3. Job advice
The only advice that I can give is not lie and not exaggerate. I see a lot of candidates that they lie in their job interview and finally the truth is shown. All the candidates must be honest about their experience, their qualifications and their skills.