I have recently been to several interviews for PhDs but they have not gone well. I had planned for the interiveiws and read around the subjects but they asked me questions i could not answer. Do you have any advise on how to prepare for interviews

What were the types of questions that you had difficulty with, subject specific or more general interview questions (you know the type, where do you see yourself in 5 years etc!)?

They asked me the normal questions of what career do yuo want etc etc, which is easy but they asked really difficult questions which were semi subject specific but not what the projects were on.

Did you read any published papers by the potential supervisor(s)? It certainly pays to do a literature search prior to interview (using PubMed or similar, depending on your field) so you can familiarise yourself with the recent work done by the group. Best of luck with your next interview.