I'm going to refer you to these books to take some of the "terrified" out of your experience:

Production Assistant

The Production Assistant's Handbook (Paperback)
by Jeff Alves (Author), William-Alan Landes (Author)
Product Details
Paperback: 118 pages
Publisher: Players Press ( March 30, 2005 )
Language: English
ISBN-10: 0887349587
ISBN-13: 978-0887349584

The Hollywood Food Chain: A Comically Real Look at Hollywood Through the Eyes of Production Assistants (Paperback)
by Tiffany Carboni (Author)
Product Details
Paperback: 138 pages
Publisher: Writer's Showcase Press (August 2000)
Language: English
ISBN-10: 0595130011
ISBN-13: 978-0595130016

How to Break into the Film Business: The Production Assistant Handbook (Paperback)
by Jeff Alves (Author)
Product Details
Paperback: 104 pages
Publisher: Players Pr; 1st ed. edition (December 1991)
Language: English
ISBN-10: 0887346162
ISBN-13: 978-0887346163

The Production Assistant's Pocket Handbook (Paperback)
by Caleb Clark (Author)
Product Details
Paperback: 64 pages
Publisher: Lulu.com (August 8, 2008)
Language: English
ISBN-10: 143575624X
ISBN-13: 978-1435756243
http://www.noendpress.com/caleb/edtech/index.php

And one additional one, my own entitled "What I Really Want to Do: On Set in Hollywood." What you'll learn in this book and no other is a blow-by-blow account of what EVERYONE on set is doing every minute of the day. What this offers to YOU (the new person on set) is a primer to how the day goes, what all the "stuff" is, and how the day's are structured so that you don't walk in and only see a lot of generic activity. A HUGE part of your job as a PA is to interact with just about EVERYONE on set at one point or another and the more that YOU know about THEIR job, the easier it will be to FIRST, be professional with them, THEN become friends with them, THEN let them know that you're available for work... IN THAT ORDER!

So, first gain their respect by at least appearing confident in that you know how a set works and what everyone does and then build relationships (genuine one's, not fake ones just to get more work) which can lead to more work down the road. Experienced crew can sniff out inexperienced people and "posers" immediately. Just go in knowing your job, do it very well, smile and be very pleasant all day long (I mean ALL day long, even until you're driving out of the parking lot that night), and the work will come to you. If you show up looking nervous, lost, not confident... no one will want to hire you again.

So, read those books as soon as you can and for a lot more resources that should be able to help you, visit the forums section at www.realfilmcareer.com and look for the "resources" threads near the bottom.

Good luck! (and RELAX!)

Brian Dzyak
Cameraman/Author
IATSE Local 600, SOC
http://www.whatireallywanttodo.com
http://www.realfilmcareer.com