Web Directory Submission
When it comes to submitting your website to directories, many times the website would have been better off never having been submitted at all. When a website is properly submitted to a web directory it can do great things for the site over time. Alternatively, when a website is improperly submitted, it tends to be a giant waste of time. Don't submit your website to search engines, just get it linked by a few websites that get crawled regularly and the engines will automatically index and deep crawl your site within a week or two, sometimes faster.
Submit manually to the major directories
Always submit websites to free directories manually. Getting your site listed in the major web directories is sufficient to increase your search engine rankings and traffic. Those listings will get picked up by all the other search engines, filtering down to mirrored directories and smaller search sites all over the net, increasing your link popularity quite a bit in the process. Submitting to these large directories does not take very long, especially if you make a list and get the required information together on a text editor (cut & paste away). That being said, there is no logical reason to risk using automatic submission tools or software that promises to "submit your site to 1000 search engines and directories". It's also a policy violation of some search engines and most directories to use automatic submission tools, which could result in your site being banned (and getting a site unbanned is no fun whatsoever).
Where to submit your website
When promoting a website, I usually submit it to the following directories: The Open Directory (Dmoz), Zeal (Looksmart), and sometimes Wow Directory. Each of these directories has a free listing option. If you run a commercial website, a paid listing is sometimes your only option. For non-commercial sites, I find spending the money on paid inclusion is a bad allocation of resources. Yahoo currently (2004) charges a non-refundable $300 to be considered for a commercial listing, $600 for sites of an adult nature, and commercial listings have a $300/year recurring fee. That money can go a LONG ways in alternate promotional methods.
How often to submit a site
Submit your website as soon as you have a domain name and a good amount of complete, live content. The basic rule of thumb is not to submit a website more than once per month, and don't submit websites with "under construction" pages visible. Different directories have different rules, however once per month is a long enough span no major directory would deem it spam.
More on search engine submissions
The subscriber's area contains additional information about using proper descriptions and keywords in directory submissions of your website, writing objective descriptions that will increase your chances of being listed, how to streamline your submission to ensure the fastest review, and resources such as smaller topic specific directories in which your website may qualify for listing.
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