This is a great question. There are a few things that I would say in my opinion that would help you during an interview .
- make sure you know about the company you are applying for. This could come in handy as you may be applying for one job and yet your skill set allow you to be an asset in the company in another area. Due some research on this before the interview. This would also be beneficial if you were to be asked the age old question of "what makes you feel that you would be a good fit for our company". If you know the company, you will be able to give a more professional answer.
- Eye contact and a good handshake go a long way.
- Dress for the job you want when going into an interview.
- Make sure that at the end of the interview, you ask for feedback. Ask your interviewer if there is anything you could do in further interviews to bette r your chances, especially if you are going to have a second interview with another person.