Is it a clinical job or an admin type job.
I work for the NHS in an office. I think it is good to do some good research about the Trust you are going to be working for, recent achievements etc. You can also ask questions about them and it will sound like you are taking an interest.
Also, really read the person spec and think of how you meet each of the things, as they will probably ask you about some of them. Have a couple of good examples ready (even if you have to make them up a bit!)