I know it might be too late but here's my 2cents about the LBS interview, in case any R3 or R4 people are still anxiously preparing:
My LBS interview took about 2 hours. Basically, it was a friendly discussion where the interviewer tried to understand my role/thinking/reasoning in certain situations. Be careful with your stories! You can of course mention the same stories you told in your application; but if so, certainly expand them. I mean, the interviewer wants to understand if there is anything more you can offer, so be ready to provide more stories.
I don't think there was a question which really surprised me. I think there are two important things you should keep in mind: 1) Know your story (the logic behind why you want to study MBA; why at LBS; what are you going to do after your studies; etc.); 2) Be honest about your experience and about who you are.
Regarding presentation, I think it much easier than I expected. The interviewer picked one topic from a list of 5 and gave me a few minutes to prepare. I do believe that the presentation is not used to test your existing knowledge on a specific subject but rather to measure how you formulate and structure your 'delivery'. Don't be too pushy rather, be convincing and strong about your arguments and back them up with proper reasoning and examples.
For this, I would recommend brushing up on how you would structure your response on the AWA essay section on the GMAT.
1. Intro - description of the argument / problem statement / position statement 2. Highlighting points the that strengthen your position, highlighting opposing points but identifying flaws in those opposing points. 3. Conclusion / closing argument / position validation
Thats about all I can think of now. Be poised / confident / and sell your love for the school! Best of luck!