Even though for many editors, the less contact you make, the happier they'll be, there will most likely be times whenever you definitely ought to call the editor.
Clarification: If you get the assignment and don't comprehend something, ask the editor. For example, I received an email from an editor to accept a query of mine, but she asked me to write the article from the perspective of a newsletter editor. I was pretty sure she has just dashed off the email rapidly and had really meant that I...