Learn about the department/hospital/trust you are applying to, learn their published values and visions and apply them in your answers. Its a bit twee and artificial, but it shows you've done your research and can apply those high level values in your answers
Have a pool of experiences that can be used to answer different questions - preferably from your time in healthcare or as a student, but it could be a previous experience outside of the NHS. The kind of questions they ask are things like "tell us about a time you made a difference to a patient" or "tell us about a time you spotted an error and what you did about it". Make sure to work those values in, and also what you learned from that experience and what you would do differently next time, if at all.
Make sure you're prepared for technical questions! "What is the definition of a Monitor Unit?" is a popular one 🙂 Also, things like "talk me through the set-up, imaging and treatment of a prostate/breast/lung/etc. patient", or "tell us about your dissertation"
Good luck!