Some information about on-site interviews:
In my firm, the goal of each interview is to find whether the 1L candidate is a match to our practice. We will ask a few conversational questions, then set the agenda for the interview. The 1L candidate has to show competencies that may lead to success at a law firm. Some desirable traits are: meticulous, methodical, and logical; resourceful; problem-solving; confident, steadfast, focused; team-building; flexible; enthusiastic; level-headed; etc.
There will be behavior-based questions that fit the model of SOAR (situation, obstacle, action and results). If you want to prepare for such questions, you need to come up with a few real-life stories (or faked ones) that demonstrate your competence in one of the desirable traits mentioned above. Give precise and nuanced answers to interview questions such that the interviewer would become more likely to hire you as a colleague. Be original.