For me I applied to the #FirstFlight Twitter Program for diverse students. Initially you have a phone interview with a recruiter and if you get passed that round you are then flown to their headquarters in San Francisco for the 2 day long event. The first day of the event you get a chance to learn more about Twitter, meet students just like you and get pumped for the next day. The next day you have technical interviews with the team you have been assigned to. To be prepared for the interview go over the basic data structures but also you just need to be yourself. During my interview I just asked many questions about my team and what their day to day look likes. They just want to know how you think through problems.