How often and through which means do we communicate?
For important e-mails (like follow-ups, documents) we use Gmail, for daily communication with the team and the customer we create a channel in Slack, where we can discuss everything that concerns the project, any time of the day. For calls and video-conferences we usually choose Hangouts.
How often do we communicate? No restrictions, we are always ready to answer all your questions and organize additional meetings on demand.