I actually did the extern program last year on the medical ICU, its a GREAT experience, so congrats and good luck! Some of the questions they ask you is
why do you want to be a nurse/ why on this unit.
WHere do you see yourself in 5 years?
What qualities do you look for in a work environment?
When was a time you witnessed something go wrong happen, and how did you handle it? Mention a time where you helped others/patient?
If you saw a coworker do harm to a patient/ break confidentiality how would you handle it?
What are you strengths?
What are your weaknesses?
If you made it passed the phone interview- you are already in good shape...just remember to be personable and sell yourself (why your a great fit for the unit) Maybe go online and research a little bit of information about NMH or the Unit/Manager you will be working with.
Also- remember to ask questions! (NOT the salary..but i think it is $15/h?) But things like in a day to day setting what is it you expect from me? What is the patient:nurse ratio, do they feel that collaboration and teamwork are utilized appropriately btw employees, what are the shifts that you will probably work (I think all units do 12hrs 3days a week but im not sure)
After the interview send a thank you letter or e-mail to show your appreciation for their time and consideration for the position, how much you enjoyed it, ect. Small thing to remember- but a MUST!
Hope this helps, let me know if you have any further questions