It is quite the rare professor indeed that will suggest a conversation on the phone or via Skype to more completely answer your questions. These are prized opportunities to be handled with care and preparation. The tips below will help you make the most of a conversation with a PhD professor whose research you are interested in.
Separate yourself from other applicants by developing a relationship with professors. It can help move you off the bubble if you are there, and can create a fan within the admissions committee. This post shows you how to contact professors while you are an applicant.