You don't often see threads that discuss how to get more Web directories in the Google SERPs. Often, you see threads complaining about how there are too many Web directories cluttering up the results. A thread at WebmasterWorld named Keeping directories in Google discusses just that.
Duplicate content in my opinion is one of the major reasons many directories are not ranking well in the SERPs at Google. So what do the forum experts recommend?
(1) User submitted listings vs. editor submitted listings: Again, I do not believe there would be a difference between the two. As long as all listings are reviewed by humans and the listings are not outright spam, the content should be fine. If you simply scrap other directories or create a dmoz clone, then you can run into the duplicate content issue.
(2) Never allow for empty directories. Let users suggest categories if there are none that fit their listing's criteria. But do not publish empty categories.
(3) Having good category descriptions help with generating unique quality content. So if you are cloning an directory, then that might help with the duplicate content issues.
(4) Don't you just love those directories that have no true listings, but what you really see are AdSense ads or other 2nd or 3rd tier PPC ads.
(5) Be creative, allow users to rate listings, add comments and be interactive with the directory.
This thread is turning into something great, so check it out. (Hows that for a call to action)