The thing that I think got me accepted is to be very focused on the main part of your job, patient care and being the patient's advocate. If you say (and feel) that way you are halfway there. Most questions they ask you can usually be brought back to that. Really try not to get too nervous, I was so nervous for my first interview and it didn't help at all.
Current issues, think MRSA, anything you know about that I expect may well come up. PALS, the relatively new patient complaints/comments/advocacy service (PALS stands for patient advisory liasion service) and again can be related back to patient care. Social issues, like someone else said, are important. I don't think it has happened yet this year, but frequently the flu and pneumonia cause hospitals to be overcowded, usually elderly patients and can cause great pressure on the hospital. This can be related back to social stuff, iepatients living in poverty, not able to afford heating, sufficient diet etc.
Teamwork, how you enjoy it, why you think you will work well in a team (highly likely to be a question), and yet as Chloe said, how you are able to work alone. You could also relate that to being a safe practitioner, that you are able to recognise your weaknesses/extent of knowledge and will not act outside of that but seek guidance. That is another statement that I feel has held me in good stead for interviews.
And, the worst of the worst, but best to be prepared for in an interview for the what are you strengths and weaknesses. It is a horrible question but so much better if you know what to say! Awful if you sit there and don't know.
Have you looked in any charity shops for a suit? Because I think it might be worth it. I wore a suit for my some of my interviews for my training, I was offered the ones I wore a suit for. I wore a suit to my last interview, and a year later the sister interviewing me commented on how smart I looked and that that was the only reason they gave me the job!! I don't know really if she was joking or not! But it obviously made an impresion. Also if you know you look good and are dressed appropriately then it will help your confidence. And if you are the only one in a suit, well then you will stand out as having cared about your appearance, suggesting the career is important to you, and will look smart! I really hope this helps and that your interview goes well. Where is it you are applying to? Hugs!