Well, a good start would be to know that if it's posted by me on YouTube, it's already in the Video Vault. Otherwise, just do a quick search here--maybe look for a key word in the thread's title. I know some duplicates will occur; we're all human and we make mistakes. But please, if anyone feels a video is important enough to post in this section, then it's important enough for you to take the time to try to avoid duplicate posts. That's just a request for everyone in general, because I'd much rather spend my 'internet time' uploading new clips than going back through, locking, and eventually deleting duplicate posts. All that being said, duplicate posts aren't really a big deal to me unless someone just starts blindly going through adding new clips without making any effort to check.
Everyone has done such a good job posting videos here so far. We have an awesome collection here. Keep it up!
By the way, if anyone has any other suggestions on preventing some of the duplicate posts, please feel free to make them here!