Hi everyone,
I'll just describe my experiences so far. In 2013, I was invited to do an in-person interview. However, a few days before my interview, they changed me to a phone interview. I unfortunately did not get a PHAP position that year. In 2013, the questions were very specific and situation-based (how do you handle this and that in certain situations). There were exactly like 5-6 questions. The challenging ones asked about how would you deal with situations relating to being a government employee, such as voting and campaigning. There are definitely the typical questions about your interest in the program and why you'd be a good fit.
In 2014, all interviews were conducted by phone. I don't really remember the questions as well, but I actually found this interview to be easier (probably because I had been interviewing and working for a year already and I already did that first interview). They asked exactly 5 questions or something again. The last question was memorable and they gave me this imaginary situation as if I was called to develop a program on a different planet - so no matter what they throw at you, take it as a public health problem and detail steps on how you go about solving the problem. There is no right or wrong answer; like in any interview, they just want to know how you think and the steps you take to come up with a solution.
If you want advice, I agree with PHAP participants who posted above. Definitely show flexibility in geographic location. Know how government employees must act and show your ability in problem solving, communication, and creativity. As you will be a federal employee as a PHAP participant, know the relationship between local, state, federal government and supervision within these sectors.
Best of luck!