Some ideas I've had luck with: Have one actionable item per email. State a question in the subject. Expect a clear answer (not quite "yes/no" but something definite). Spend a short time (one or two paragraphs describing the question in detail, but don't make it longer than that.
End the email with the question in the subject asked again.
EDIT: If you find that you need to have a conversation, either walk over to their desk or pick up the phone.
End the email with the question in the subject asked again.
EDIT: If you find that you need to have a conversation, either walk over to their desk or pick up the phone.