Domain Name Age of the domain Web Directory slogan Backlinks, page rank , page strength template and nav Design SEO friendly url and pages submission option. Search engine stats and Alexa rank and demographic number of links on a page payment options promotion budget articles blog web tools
1. Well maintained, without dead links 2. No spam, and descriptions and titles that look well-written 3. Visibility 4. Design 5. A good price for the traffic or SERPs boost it will deliver 6. Originality, something about the directory that's a bit different from all the clones
I'm fond of most directories that exhibit some form of editorial integrity - those that don't just accept anything and everything anywhere and everywhere.