Go in keeping these tips in mind, and you'll be an irresistible candidate!
Do your research
As SOON as you accept an invitation for an interview (actually, even before accepting...) you should know the ins and outs of the company. This doesn't just mean looking through their website for 15 minutes and write down something you found on the "About" page to bring up during the interview. Dig deeper! Did The New York Times cover a story on the company? Did the company just start a new project? Are they merging with another company? Did the company just get a new CEO?
What's even more impressive is if you have personal connections. This doesn't mean you need to be best friends with someone on the board, but maybe you have connections through other people. Ask your network. Go on LinkedIn and see if employees in the company you are interviewing for are connected with your network, and if they are, reach out to the mutual connection! Typically, mutual friends are more than happy to help.
Dress the part
Let the company picture you there. While you're researching, take note of what employees wear on a typical day at work. Someone that works at JP Morgan is definitely not going to be wearing the same thing as someone employed at URBN. Take what you see and take it up a notch. Let the interviewer know you care about your appearance.
That being said, don't wear anything so out of the ordinary that it'll distract the interviewer. Sure, you want the interviewer to remember you dressed nicely, but you really want them to remember what you said you SAID.
Ask what the company can do for YOU
Why suffer going into work everyday? There are tons of companies out there that have incredible work culture and benefits. You should enjoy where you spend half of your day! Ask the interviewer what the company culture looks like. Ask what people enjoy most about working at the company, and what makes it distinct. Ask for other opinions as well from other employees. Again, LinkedIn is a good source to use for this. Make these connections and form relationships. The more genuine and interested you seem in the person you reach out to, the more honest and happy they will be to fill you in on what they like and don't like about the company they work for.
Know your weaknesses
This question comes almost every time, or at least one type of question that requires some sort of "negative" answer. Everybody has weaknesses and everybody has made mistakes. Tell them something you genuinely aren't good at and HOW YOU ARE TRYING TO GET BETTER AT IT. Don't turn a positive trait into a negative one. Recruiters and interviewers know that trick. Pick something that sometimes gets in the way of succeeding, and own it. Laugh about it! Nobody is perfect, and these employers know that.
Also, don't choose a weakness that is related to a skill in the job description. For example, if you're applying for a secretary position, don't say you're disorganized. Your interview probably will not end well.
They really just want to know that you're aware of your weaknesses, and that you have a game plan on how to improve them.
Be aware of body language
Actions can speak louder than words, even in interviews. Make sure that you look engaged in what the interviewer is asking. Use hand motions when giving certain answers; it makes what you say seem more authentic. And of course everyone's favorite: eye contact. Let the employer know you are listening! You don't have to look straight into their eyes; some people will look at noses or foreheads to make it a bit more comfortable. Show you are confident in what you have to say!
When the interview is done, that doesn't mean the process is over. Impress these people by writing them a thank you email, or better yet, a hand written letter. My capstone professor who used to recruit said that if she was stuck between two people to hire for a position and one wrote her a personal thank you letter, she would pick that person. (More people do this than you think!) Bring up something unique you talked about in the interview so the letter seems personal and authentic. A little letter can go a long way!
Show them what you've got!