I'm a college student, so there were two rounds of interviews. First, you apply online and get pre-selected for an interview. The first round was a 1-on-1 interview on campus after an info session. Go to the info session - the recruiter tells you pretty much everything you need to know about Marriott and what kind of interview questions they ask. It's STAR format (Situation, Task, Action, Result), and they really press for the result. The first interview was about 30 minutes, with basic questions including geographic preference and which department you want to work in and then STAR interview questions.
After the first interview, you do an online questionnaire. This is a personality questionnaire and takes 30-40 minutes. It's a standard "are you cheerful" and some basic situation questions. "Sally is doing X, what would you do in this situation?"
After the first round interviews, they email you in for the second round interviews. For the second round they send you to a different city and put on a 2-day event. They go over all the compensation and benefits you will receive as a Voyager and have a Q&A session with previous Voyages and Management Trainees. Afterwards, you go to a reception with GMs, Directors, and Regional Directors from all over your region. This is your time to meet with them, network, and meet your interviewers for the next day. They do not tell you who you will be interviewing with, so you have to try and get to as many people as possible. I didn't meet mine beforehand, but that's alright. The interviews are 2-on-1 all the next day and they last only about 20-30 minutes. It's just 3-4 STAR interview questions and then you have time to ask them questions.
Make sure that you have good questions prepared! Think of actual questions about the company or interviewers you'd like to know. I had a wonderful conversation with my interviewers just by asking questions I was generally curious about. Think about areas of hospitality that are important to you, things you want to accomplish in your first year, and base questions off of that. Asking "Is there anything that you felt I did poorly?" or "What do you like/dislike most about Marriott?" are very standard questions. Really spend some time on this part, it's one of the most important parts of the interview.