I attend a target school, so I was able to speak directly with the recruiting manager and a few consultants (through information sessions) before applying. Once selected for an interview, I did so at the local office before a final round at my office of choice:
Round one (two interviews: 15 minutes of fit, 30 minutes of case) - The interview begins as soon as your interviewer picks you up from the waiting area. Start making conversation right away! As soon as we sat down, my interviewer already started to make comments on her notepad from our interaction in the hallway. Both interviewers had no unexpected questions, if you search for "fit interview questions" on the internet, and read through them, you'll be fine. Although, my second interviewer did try to give me a slight stress test with 3 or 4 "what else" questions, but nothing more intense than that. Cases were a lot more simple than the practice cases, if you're breezing through the LBS casebooks, you'll be fine. Each one had 1-2 exhibits with very straightforward math. Try and be friendly, and work some humor into the conversation and you'll be fine.
Round two (same format as first round, with a written case preceding one of the interviews) - The case interview was not as bad as expected. You have 45 minutes to read over the material. Treat it like a normal case...read over the prompt and identify the question, spend 60 seconds building your framework and deciding what you'll need to know to answer your question, use 5 minutes to go through the slides to read titles and decide what you'll want to keep, spend another 5 minutes digesting the slides you deemed worthwhile, spend 10-15 minutes diving into those slides and calculating anything you may need, spend 10-15 minutes building your story/answer, spend 5 minutes practicing your story, and take any additional time to review the slides one last time for any additional insight you could add now that you have an answer. After that, the rest of the interviews are pretty fun in this round. Regardless of what happens, they want you to walk away with a good impression of the firm, so you will have fun in this round. The people are extremely nice and the fit questions are well within you comfort zone.