Off page Optimization is a backend process for SEO.Its fully based on Link Building.Google Find Our Site From Previously Indexed Sites.So We Have To create Link From Other Sites.there are many ways to do that.basically to ways.

they are.,
1.Create Free Links.
2.Paid Links.we have to pay for that links.

mostly use free links.How to create links from Other sites.that is submitting post about Our site in that site.and give out site URL in that post.They are more link building strategies .they are.,posting in

1.Article submission.
2.Social bookmarking.
3.Classifieds submission.
4.Directory submission.
5.Press Release.
6.blog comments.
7.forum signature.
8.RSS feed Submission.
these are important factors in Off Page Optimization.

learn more....http://www.seomoz.org/ugc/21offpage-seo-strategies-to-build-your-online-reputation