I applied for an internship with PwC through my schools career services. They contacted me via email saying them would like to do an interview on campus. Fairly easy, low pressure. Spoke with the tax partner who gave me an overview of what its like at their office, what their culture is like, etc. Asked basic questions about my availability, some questions about my resume. After that I was contacted via email asking for an office interview. The office interview involved mini-interviews with each member of the tax department, each having questions to ask you about your past or how you would handle a particular situation.