"Team Spork" - What a great name!
I know you asked for 2, but here are the top 3 rookie mistakes, in my opinion:
1. Not using the available free help & training resources (this site, other 3ds Max forums, YouTube tutorials and
http://students.autodesk.com).
2. Not reading the rules thoroughly. There are very specific requirements for file type, video length, titling, copyrighted music, etc. It's heartbreaking to hear about a rookie team that put hundreds of hours into their animation only to have it disqualified because they misunderstood a rule.
3. Trying to model & animate humans. This is very difficult and without a lot of experience they end up looking & walking like zombies.