I haven't interviewed law yet.. so.. take this as more "general" interviewer advice (I used to interview people in my past life as a technologist).
1) remember, if they don't hire you, someone else will.
2) if you don't like the interviewer or the job, try to relax into the interview, since it's a dead letter anyway - and maybe once you relax they will too.. then things can happen.
3) if get the taste of death on an interview - might as well ask if there's any advice they might have for you about your interviewing - hell, that's flattering anyway. (Last time I asked, my zipper had been down through the whole interview... DOH! But they did call me back for a second round.)
Some of these are chancy - if you're wrong and they really do like you, 2 or 3 could put you out of the running. But.. most definately, just try to relax. Nobody likes interviews in my experience. They're too brief and too imposing to really understand a person - and your best bet is to come out looking professional, knowledgeable, and humble.
Just to restate - these weren't law interviews - I don't have a feel for the differences yet, so your mileage may varry.