Directories have been good sources of one-way links for a long time. It is a one of the easiest link building method especially for newer sites. But quality is still the name of the game. Some pointers in selecting the directories to submit to:

High PR - indication that Google sees some value in the directory.
Well maintained - listed sites are in the proper category
High Traffic - getting traffic could be minimal from directories, but majority are targeted
Kewords ranking high in SERP - Well optimized, shows that the directory is well-marketed and SEO'ed.

Which to avoid:
Link farms that pose as directories
Directories that require reciprocal links
Crappy ones with crappy sites listed

What are your thoughts? Care to add more pointers?

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The #1 Marketplace for Webmasters | Web Design

I would agree in that its very important to find good directories (Like google's directory) and make sure they are respected. I think searching google just as a start will do, also yahoo's directory is a nice place to add your site to. In general, its not that hard to spot a really bad directory, just look around before you add your site, thats my policy. Then if I'm not sure, I ask some people I know are knowledgeable or just some friends to see what they think.

A great place to start is once again, http://www.google.com/dirhp, google's directory.

Good points! Also, another important pointer is whether a directory rejects certain submissions - this is a good indication as well that the directory is well maintained.

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The #1 Marketplace for Webmasters | Web Design

Good points there.. I am trying to put following factors into my list:

1. Alexa ranking
2. PR
3. Number of indexed pages
4. Number of backlinks
5. Are 'crappy' submissions rejected or they accept EVERYTHING
6. Review time.

When I do directory submissions, I try to search for some important details about the directory such as it's age, number of IBLs, the sites listed, PR, no-recips required

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Traffic is also a primary concern for me. Alexa and quantcast should be able to provide rough estimates on how well a directory is traffic-wise.

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The #1 Marketplace for Webmasters | Web Design

I submit to all directories, low PR directories will accept your link more readily and they have a good chance of getting high PR in the future.

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Yurts builders and hire service == Free Directory Script

Thanks for the pointers

Good points! Also, another important pointer is whether a directory rejects certain submissions - this is a good indication as well that the directory is well maintained.