After latest updates i am sure that previous methods of link building isn't working like social bookmarking, comment, forum profiles etc. Now
I started cleaning up some spammy or low-quality links, I also posted some articles on article posting websites.But I posted duplicate articles in many article posting web site with my site's links in those articles. now i really don't know whether should i remove this article or not ? to recover form Google penguin 2.1(May 22, 2013) update. Now i want to start link building, After searching hours of time i didn't find in 300 pages where the link opportunity available.
Where do i start links i don't want to make thousands crappy links, just want to make few link but they should really powerful.
Currently my site rank down in Google search result page compare to before Google penguin 2.1(May 22, 2013) update.
My website is eCommerce it has little bit more competition in search ranking.