Just finished my first user interview yesterday and a few things came up that I thought other practitioners might benefit from.
Reviewing the current state of the site went well - lengthy and detailed discussion, focussed on page outcomes with only a skeletal set of prompts needed from me. Started by using the home page which was outside the scope of the project and I found that following discussions on the in-scope pages went faster as the interviewee was aware of the topics that I was interested in, and approached them straightaway.
We have a set of proposed changes to pages that we came up with here - I went through these asking the interviewer just to stop me if they felt strongly about something. Make sure that you really separate yourself from your feelings about the project (not easy if you've been working on it a long time) - avoid the temptation to say 'you agree with this idea, don't you?' because any assent here would be based on pressure rather than a real recognised need.
My point here is that the project will need to prove that it didn't try to gain a mandate for something which wasn't volunteered by the interviewee. This could be in the form of expanded quotes from the interview which are approved by the interviewee, and reporting on whether a planned improvement was already on file before the usability consultation process took place, or a ranking system. Whilst this point is quite fine in nature, it signals whether the investigation is truly objective in practice.
And, if you can, record the interview and play it back whilst you are writing up the notes as it's easier to reflect on the sense and meaning of the points made. In addition, you can rate your own performance and think about other ways to pose questions to make interviews a more powerful part of your toolkit.