Every candidate has two interviews. The first one is 1:1 with one of the RLCs (professional staff) and a current CSA, and it usually takes 20-30 minutes. You'll be given a sheet of paper with several questions, a few minutes to look them over, and then they'll start asking. It's very conversational, they'll want stories/examples from your life.
The second interview is a group interview, and it'll involve icebreakers and a lot of discussion. It is NOT in your best interest to make other candidates look bad during teh group interview; be polite, encouraging, and don't dominate the discussion too much.