There is few things which is essential: links links links:)
From:
1. Forum threads/posts
2. Blogs
3. Forum profile links (highly discussed recently that they don’t work anymore, but links still show up nearly every day in my case)
4. Articles (hubpages, ezinearticles and few more best ones). Don’t submit one article to tens of sites as this won’t work
5. web2.0 (squidoo)
6. Directories (good only in a long run in my opinion)
7. Social bookmarking (works well)
As others said in previous posts, contect works best these days…
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