The process took 1 day. I interviewed at New York Post (New York, NY) in Jan 2012
Interview
I submitted my resume through my University's career services website and an HR rep called me the next morning. She was friendly and asked me several questions mainly about why the Post and why sales. She then invited me to NYC to interview with them in person and told me I would be interviewing with 3 people, herself, a more senior HR person, and a senior account exec. Once I was in NYC and at their office, the same woman interviewed me and it was one of the strangest interviews I've ever had. She was asking me questions, that genuinely weren't questions, I had no idea what she was saying. She would just kind of stare at me, and when I would answer, she would ask something weirdly unrelated. After her, I found out that the more senior HR person was out of office and I was walked to the account exec's office. He was in a meeting so I was walked back to the waiting room. He came and got me and interviewed me. He was also a different person than they told me I'd be interviewing with. I thought the interview with him went well, although he seemed to be unfocused on me and acted completely unprofessional towards one of his employees, pretending to strangle her in front of me. They seemed totally unprepared for me and just kept dropping me off in places that I didn't belong. I was told I would hear back soon, which I did, that I was not a fit. I would firmly agree with their decision.
Pretty straight forward interview process. You'll meet with people throughout the company, and someone will inevitably ask you to sell him an item on his desk or something hanging on the wall. They'll want to know that you're a fan of the brand.
I applied through college or university. I interviewed at New York Post
Interview
They first did interviews at my career center (two 30 min interviews). They were very nice and friendly, and pretty much run through your resume and ask why you want this job and company. If selected, you will go through what they call "HQ." It is 6 back to back interviews (about 35 min each) in New York, meeting with various sales higher ups and management. They do not ask many difficult questions, but you must be prepared to answer why sales, why sales, and why sales. You have to convey to them that NYP advertising sales is your dream job or else you will not even be taken seriously.