I've had different types of interviews, from the generic what are your strengths & weaknesses, to clinical questions where I was drilled for 45 minutes on critical care patients, sometimes they look @ my resume & must like me because they'll just tell me about the unit & say I'm hired. It really varies. I am not a good phone interviewer and get really nervous actually, but I haven't had anyone decline me from an interview. Phone interviews are definitely better than in person interviews!
Mention that you are flexible and you are a team player. Say you have a positive attitude & work well with others. Tell them you ask questions if you are unsure of things, like you'd ask the charge nurse or another nurse for their opinion. I'd imagine a manager wouldn't really want someone who wasn't flexible with their schedule too. I usually just tell them I'll work whenever you need me. If you do have a vacation or something planned, make sure you bring it up during that interview.
Also not sure what area you work in, but most managers have asked me some clinical questions. Think of a difficult patient you've had and how you've handled that. If I can't think of one I just think of my last week of work and what happened and I'll talk about that. I remember my last interview she asked me about sepsis, like what orders I'd see, etc.. If you're ICU I'll give you more examples, let me know. If you don't know something it's ok. I've not known answers to questions and have still been hired.
Write down questions you have for the manager. They'll usually go over it. I usually ask the manager about orientation - how many days of hospital orientation & how many on the floor (hopefully 2 days on the unit), and where will I float, do they have any other travelers working, why do they need travelers, etc..