I attended a small conference by NI hosted at my University. I really wasn't all that interested but, after the talk, they were having interviews. The questions in it were very basic however, I know from a friend you had to have a minimum GPA to even have a shot. After that, I was asked to fly to Austin for a day of interviews and such. Like many other companies, you get interviewed by up to three different teams, each team has 1.25 hours with you where they ask both, technical and behavioral questions. After this is said and done, one last interview takes place for any concerns and questions you may have as well as routine questions for finding the exact match from the candidate's point of view.