Good luck! Here's an idea that worked for me(interviewed for 5 positions, offered all of them). Besides the basics of researching the hospital, mission and unit, it is a good idea to bring nursing school care plans that you have done, preceptor paperwork that shows that you did well during your preceptorship. Any favorable written comments by other nurses during your clinicals.
Provide references by your instructors, if you have had good attendence let your interviewer know because this is very important. Also research the questions that you will be asked. There are many good websites that offer this and I found when I researched a hospital that I applied to, they many times had a listing of the interview questions that would be asked.
Appear confident, and let your interviewer know that this unit is exactly where you want to be. Ask to be shown the unit and use terms like "Is this the room where I would be gathering my supplies" you know-like you are already part of the team.
Good luck and God bless.