If you have been asked to come in for an interview it obviously means that the employer is interested in your profile. However, you are going to be part of a group of chosen candidates and so the interview process will allow the employers to sift you out from them. Therefore there are some things you should think about before your big day.

1) Get to know as much about the company as possible before hand so that you can slip in a sentence occasionally. This will make a good impression on the interviewer.
2) Make sure you are dressed for the occasion in formals.
3) Go in with a positive attitude but make sure you are not over confident.
4) Procure a list of questions that employers usually ask and rehearse a bit so that you don't fumble.
5) Make sure you are on time. Being late for an interview will reflect on your personality and you will come across as disorganized.
6) Make sure you carry all relevant documents including the cover letter and a copy of your resume.

Getting to the interview process is not going to be easy. There will be a lot of job hunting you will have to do before hand. A lot of people nowadays prefer using online portals like Career Builder and Monster. In order to search these sites properly and make sure you get an interview with the best company you can get yourself a job search software which will allow you to go through all these online portals at once with the help of some keywords and will also allow you to set up alerts that let you know when there is a new opening that matches your search criteria.