Before submitting your site to a directory, do a little bit of research on the directory.
• How old is the directory? The older the better.
• If the directory has a PageRank of three or higher, then it is more likely to be trustworthy.
• Does the directory charge a fee? If it does, what do you get for the fee? If you just get a link in the directory, then it is probably not worth it.
• Is the directory based in your own country? Getting listed in directories that are not in your own country is generally a waste of time, although there are some exceptions e.g. the DMOZ.
• Are submissions reviewed manually? If submissions are not manually reviewed, the chances are that it is not a good directory to be listed in.
• Does the directory rank well in the SERPs? If there is no sign of a particular directory, then it is unlikely to be worth the effort listing in that directory.
• How often is the directory crawled? In the SERPs, next to the URLs for the listings, there is a tiny inverted triangle. Click on this and then click 'cached'. You will then see a cached version of the page as well as information on when it was last cached. If the last cache was more than a few months ago, then the search engines are not too interested in that directory and nor should you be.
• Does the directory look like it serves a purpose? If the directory seems to be nothing more than just a bunch of links, then it may not be an ideal directory.
• Does the directory contain broken links? If the directory has links that do no work, then it is probably not well maintained and not worth the effort of submitting to it.