It is doing SMO so that you bring constant traffic from social media
Be clear with your question, are asking for social bookmarking
or just want to know about social media optimization
Interesting contents will help you get constant traffic! So work on contents too.
Thanks for share such ingratiation.
Try some more activities like social media share,blog post or article.
I suggest keep doing quality work on high PR Social bookmarking sites.
If you want to gain genuine traffic for your business, social networking is the best option.
Social marketing from various sources like Facebook,twitter,instagram or linkedin are best platform.