When I got called in for an interview the first thing they had me do was go to human resources and take a written exam. The exam consisted of about 150 questions, 75% maintenance questions and 25% math questions. The math questions were easy, I would say at about a ninth grade level. The maintenance portion was pretty broad. They had electrical, hydraulic, welding, and mechanical questions. They weren't necessarily easy but you only need a 50% to pass so it's not hard to make it to the face to face interview.
The face-to-face interview was a panel style type interview. I sat at a big table with three of the supervisors. It seemed like they based most of the questions off of what I put on my resume so if your resume says that you have a certain skill or know a lot about a certain piece of equipment be prepared to answer technical questions about it.