Global Game Jam currently maintains a large Slack group for all site organisers, regional organisers and the executive commitee team. Chances are if you have any question, someone on the Slack group will be able to help you. It also gives a great oppertunity to connect with other volenteers organsing GGJ events.
It is important at the very least to check into the Slack channel at least once a week, and check into the #announcements channel, so that you don't miss anything important. You should also set up your notifications so that you received emails if you get sent a private message, or your name gets mentioned, as it is used as the primary communitcation tool for the GGJ central team.
You will receive an invite to the Slack group once you have had your phone call with your regional organiser.