The best way to prep is a mock interview with an experienced PM. I had the opportunity to do us through the career center at my business school, and it was super helpful.
To prepare for that, I'd recommend:
1) books such as Decode and Conquer and Cracking the PM Interview to help you understand how to break down product problems
2) YouTube videos of mock interviews. There is a lot of great content out there, especially on the product design/sense and execution case interviews.