In an interview the person(s) conducting the interview have a set of goals that they wish to achieve. These goals include;
1) indicators of expertise and competence:
Your education and past work experience will have a big impact on this criteria. To have gotten an interview implies that you have met the minimum standards required which they would have taken from your resume.
Whilst skills and expertise are very important, they are of little use if you are not motivated or interested in doing the job. To show that you are interested and motivated in the job is important because the employer wants to hire someone that will be happy in the job over someone that won't. If you are enthusiastic about a job then you are more likely to stay longer making the time invested in you more worthwhile.
3) interpersonal skills:
To be able to fit into the work environment is very important. You could be the best Project Manager in the world in theory but a pain to work with so much so that it makes other people's work painful. Do you work well in a team? Do you work well under supervision? Do you supervise others well? These are all important factors that will be taken into consideration when the employer is hiring for a managerial role.
4) decision making skills
Will you be able to distinguish between those situations where innovations required and those where established procedures must be followed? Can you quickly deal with a situation by analyzing the nature of the issue and taking appropriate action that incorporates alternative courses of action?
5) interest in job
Do you really want this job? Is this what you want to be doing in 5 years time or did you apply for it on the off chance you would get it? Employers want people who are genuine because that means that the level of effort will be higher.
6) personality and likability
Do you listen well, give positive verbal and nonverbal feedback, have a pleasant and enthusiastic manner, and demonstrate a sense of humor and smile?
7) personal presentation
Did you dress appropriately? Did you groom properly? Did you smell good? Did you look the part? First impressions last, so make it count.