Today an editor emailed me with a simple question. At the end of the email, she included her phone number and said I could call her if I preferred the phone to email.
While my instinct was to email her so I wouldn't bug her with a call, my freelance writing mentor Linda suggested that I call instead. That way, the editor would hear my voice, and our relationship would form quicker. (I ended up getting her voicemail. But hey - she still got to hear my voice)
Linda's tip: be friendly, but keep the call under 5 minutes.