This usually backfires and is counterproductive. You are simply after information. Shake hands, eye contact. Convey a sense of competence, calm, non-threatening. In a restaurant, pick a table away from the kitchen.
Phones are a distraction in the office.
Get interviewee's undivided attention. Avoid getting in debt to your source. Pay your share of everything. Start talking before you produce your notebook or tape recorder. If you have to wait for your source to get off the phone, look around the office.