First of all, congratulations on getting the job!
I have some film experience, and from what I remembered the first AD was the loudest person on the set
Before the shoot, the Firsts' main task is to create the filming schedule with the Director. When drawing up the shooting schedule, First ADs must also be aware of budgetary constraints, cast availability and script coverage. Preparing the storyboard, overseeing the hiring of locations, props and equipment, and checking weather reports, are all key pre-production duties for Firsts. (I remember always checking the Weather Channel's hour by hour weather)
First ADs' core responsibility is to keep filming on schedule by driving it forward, so they frequently make announcements and give directions to co-ordinate the cast and crew. They also control discipline on the set, supervise the other Assistant Directors, and oversee the preparation of the daily 'call sheet' (a document detailing daily shooting logistics, which is distributed to all cast and crew). Firsts are also responsible for health and safety on set or location, and must take action to eliminate or minimise hazards at all times.
So it's alot! I think if you did a quick Google search you can find books that can help you more.
