In order to prepare yourself for an interview it is important to think of the questions a potential employer will ask you and also to " work out" what your answers to those questions will be...
The ultimate interview starter is, "tell us a little about yourself." You should have a 30 second answer to this question prior to going into the interview, or at least a general idea of what you want to say. The answer to this question can sometimes set the theme or mood for the entirety of the interview. If you want the interviewer to know you are a family oriented person, make sure to discuss this. If you want the employer to know about a particular job you had in the past that really made in impact in why you are where you are, this is a great opportunity to talk about it.
Big piece of advice: don't get too personal. This is an interview, not a counseling session. You want the interviewer to get to know you on a professional level...nothing more. The last thing you want to do in an interview is make your potential employer feel uncomfortable. Getting too personal has a tendency to do just that. Think of your interview as a first date. What is the conversation like? You talk about your background, your family, your previous employment, your hobbies, etc... What topics do you avoid on a first date? You avoid the 4 B's (hopefully): Bible, Booze, Barack, and Bad Experiences.
Bible & Barack - You don't want the topic of conversation to spin to your religious or political beliefs because you have no idea what your employer's beliefs are...unless your job is working for a particular political/religious affiliation you should avoid these conversations.
Booze - don't talk about what you drink, the amount you drink, where you drink, who you drink with,...just don't go there.
Bad Experiences - An interview is a positive moment! Keep it that way. As soon as you complain or talk about how difficult your life has been, the interviewer takes that information and may come to the realization that you will just complain about this job and how difficult this job is, and won't hire you because of it. Don't put yourself in that situation.
Here is a list of potential interview questions that you should take the time to think about how you would answer them, taking into consideration the advice above:
What are your strengths?
What are your weaknesses?
Why do you want this job?
Where do you see yourself in five/ten years?
What attracted you to this company/firm/agency?
Why should we hire you?
What did you like least about your last job?
What were your respondibilities at your last job?
Tell me about a difficult situation you encountered at a previous job and how you handled it.
Are you willing to re-locate?
What are you looking for in a starting salary?
Do you have any questions for me?
Finally, enjoy the interview! The interviewer may have had 50 applicants and is interviewing 15. Keep that in mind and know that you and your resume made the list. That is something to be very proud of!