I think the most important thing to realize is that your interview is simply a conversation in which the firm is trying to determine whether you would be a good fit in their company, while at the same time you are determining if the firm is the right fit for you. So relax, be yourself, and ask valuable questions to help you get to know PwC and PCS Tax. As for specific qualities/experiences (and I think these go for any interview in this field), I would say leadership and teamwork are two qualities that are highly valued, and it is likely your interviewer will ask you to touch on both of these areas. Within PCS Tax we were constantly working with others on engagements, which is why teamwork is so important. They are also looking for people who already have leadership qualities. Even when hiring for Intern and Associate positions, they are looking for candidates who are leaders among their peers, and candidates who would be great Seniors, Directors, etc. down the line.