I applied to 6 schools total and reached out to faculty members at all 6. Some faculty were more responsive than others - some responded saying they don't talk with students until they are accecepted, while others were very helpful and encouraging. I had phone conversations with 1-2 faculty members at all but one school, and met with a couple of others if it was convenient. Unfortunately, many of the faculty whom I met with do not serve on the actual admissions committee, so it's hard to say how much it will help the admissions process - I just reached out to faculty with similar research interests. In retrospect, if I had more time, I would have visited more schools while applying to meet in person.
I didn't apply to the school where I received my MPH, nor do I currently work at a university, so I don't feel like I have any strong connections to faculty members at my schools.
Thus far, I've been waitlisted at Hopkins, had interviews with 2 others schools (have yet to hear back), didn't receive an interview at Harvard (assumed rejection), and the other two schools (NYU Wagner, GWU Trachtenberg) don't conduct interviews.