Whilst this particular thread is aimed at the Top 15 factors when selecting a paid directory, they are nonetheless useful for selecting any directory in which to submit your website. On the flipside, here's an easy way to avoid bad web directories... What I would look out for as big red flags which are warnings NOT to submit: Anything that uses a default template. This is a non-unique design and comes with free with the script. If the design doesn't include the directory name and has anything like "My Directory", "The Directory", or "<script-name> Directory" then that's usually a dead giveaway. Anything that is duplicated. Directory owners often think more is better, and they couldn't be more wrong. If a directory owner, owns half a dozen directories that all look the same. That's a big warning not to submit. Anything that uses .info Why? Because they are cheap, and therefore easy to discard. A directory owner that cares about their directory will get a proper name and brand it (which goes hand in hand with design). A directory owner that doesn't care will get a cheap .info or 10, and then drop the domains when their directories all fail Anything that has redirected outbound links These aren't useful and can be dangerous, especially if they send you to malicious websites There's probably half a dozen more red flags I could point you too, but seriously if a directory has any of the above, it'll have all the other red flags as well.
The two things I've found as my top criteria for a web directory are: 1. In your niche (relevance to your site is very important to google) 2. The category page where you'll be listed is indexed in google (the higher in the SERPs for text on the page the better) There are a lot of lists out there with directories. Start with them, but check how it ranks in google before you submit and it'll help your site the most in the long run.
You can check for its PageRank (authority), Alexa (traffic) and the quality of sites it allows (by random visiting a few of them) etc.