Forbes -- Interviewing Effectively:

As you start preparing for the next major events in your life - your first part-time job, college applications, a full-time summer position - the biggest common denominator will be interviews.  These can certainly seem stressful, especially to anyone who hasn't had much (or any) practice with interviewing.

With that in mind, Forbes has compiled a list of ways to interview effectively.  They are certainly worth taking the time to read...  (link here).

The point I want to stress here is: be professional.  Even if you are just trying to get a 10-hour-weekly position as a bag-boy at the local grocers.  Professionalism and Respect are key points that companies look for - since you will essentially be a "face" that their customers put with that company's name.

You only have so many minutes to make a great impression during a meeting or interview and then that's it.  First impressions are key - you will most likely not ever be able to go back and fully repair a bad first impression.  That means no cellphones, or texting, or chomping on gum, or cursing, or flirting, or anything else that is generally considered unprofessional in the work force.

Remember that you do have skills to bring to a position and a company.  You do have value.  Now, go do your research and get ready to ace that interview!