Since: Apr 2011
Since the rules have been opened up a little to allow the potential use of stock footage and other types of pre-shot fotoage it's probably worth thinking about copyright.
The terms of the competition require that you have proper rights to everything you use, so be very sure that you do, and be prepared to prove it if you're challenged.
This means, if you're using a stock footage library of any sort, make sure you check their usage guide to make sure you're in compliance with whatever terms they have. If they require a credit, make sure you provide the credit, otherwise your license to that footage may be invalid. Save details of payments you made to them or whatever else might be necessary to prove you had a suitable license to the content.
If you are relying on Public Domain content - double check that it is in fact in the public domain. US and NZ copyright laws vary. While US laws are usually more restrictive in terms of when and how things enter the public domain it's possible that something that is public domain in the US or elsewhere might still be protected by copyright in NZ. Save details about where and how you found the content.
Don't trust Google or any random websites. If you find something on a random website, YouTube or on a Google search that says it's free or public domain, don't just take if for granted. Try to verify it - check for proper creator attribution and copyright info. If it seems sketchy or a little too good to be true, err on the side of caution and don't use it. If you do decide to use it then, again, definitely save details of where and how you found it.
Copyright is a huge pain in the ass when using content made by any third-party so be very sure that you have the rights you think you have, and that you can back up your belief if challenged. Where possible credit everything you use with a source so that there's no argument about how and where you found it.
If you're using something that you have made yourself in the past, just make sure you have the rights to grant yourself. If you shot something for a client, or as an employee, you may not have the necessary rights anymore. If you made something and then licensed it to someone else it's also possible that you don't have the rights to use it without their approval. If in doubt, double check!
Chances are you won't run into trouble, but 48HOURS organisers have to protect their interests too, so if they have any reason to be concerned they may well come to you for clarification.