I've had around 25% of my traffic from google this month (~6k visitors) - most of it comes from people searching for things which are listed in my directory rather than searching for "free directory" or something similar.. I've also realised that I seem to be sending a lot of traffic to other sites too, people will search for a topic on google, end up at my directory on one of the listings pages and then click through to the site they are interested in..
I don't believe in submitting sites to search engine not even to google. when you start building backlinks to your site, the search engines will find you. but if you want to do this, you can manually submit your site to the big search engines like google, yahoo and bing. and to the local search engines if your site is in chinese or russian for examlple.
Whether you submit to search engines or not, it's still going to take several weeks to months to see your site show up in the search engines.
Search engine submission is a process to submit a new website directly on search engines. Search engine submission may be helpful for the website's fast indexing on search engines.
If you are doing SEO for your website then you have to focus on both On page techniques as well as Off page techniques which will helpful for website traffic, website ranking through different search engines as well as business leads.