"I've got an interview coming up at a design firm that I really admire. Any tips for nailing the interview?"
The work has to be done beforehand so can make sure you will get the job. If your work is good and you are likeable, you have a good chance in any interview. Stand out by having an opinion, asking questions of the interviewer and being able to connect on other things outside of design.
People want to work with people they like. However, the biggest factor is doing your research into the company and who is interviewing you. Read up on their social media profiles to see what makes them tick - sports teams, films, food, pets etc.
Win their head with your work, win their heart by connecting on personal passions, then you'll put yourself in the best position to get the job.