what stragty is used behind the seo working?

on-page seo: sign up to google webmasters and they have plenty of resources to guide you.

off-page seo: a good link-building strategy with social networking

The rule is simple, everyone knows to tell you that you need to build as many links as possible and have unique content. But there's more of it. You need to monitor the number of daily links you create and make sure none of them will harm your website.

You can do a lot of reading for free and you will easily learn the basics of SEO.