I think that qualities that more impress an interviewer are work experience and personality. The appearance is important overcoat when you attend public in your job. In other jobs, appearance is important too, but I think is more important work experience, because experience gives you skills to unwind in a lot of situations. The personality is basic too, because your character determines for example if you are be able to work in group, to support stress, to deal, etc. About qualifications, I think that you must have a degree to do some job (it isn´t necessary in all jobs), but qualifications don´t guarantee that a person does his job well.
I have been interviewed for some job. The experience has been good. The common questions are about your work experience. I don´t like when interviewer ask me about my personal life, because I consider that it isn’t subject of interviewer. In spite of that, I comprise that interviewer is interested about your personality, because depends on that, you will be fit to do a specific job.
To go for an interview, I advice to go well dressed, to be punctual and to be polite. You must to be sincere, but you mustn’t to explain things that interviewer don´t ask you because that could damage you if you don´t know what specific job are offering you.