I do not have the time to go into details, but maybe you have noticed that things have changed in SEO. If you get some PR backlinks to a (new) domain, it will not help much. If you try to push it, it does not necessarily works.
If we talk about PageRank and buying "strong" links from authorities, maybe PR6 or PR7 links to your website or blog, you can be a blowhard to your friends and say: "Yes, I am a really cool man. I did it again." But somebody else hits you in your ranking, even with your cool bought links.
If we talk about Anchor text in External Links, you can try to push a site. And it works a little bit, but not comparable to the past.
And some still trust in keyword density or keywords on a page. Cool. But: Does not work.
For years now SEOs talk about TrustRank. I did it myself in this blog many times in 2007. And now the time has come. More than ever for some weeks now.
As ever some German SEO thugs will not trust my words and may attack this post, as they did for years now, so you should spend about 20 minutes of your time in this video and the link below it:
Read it: How Google's Rankings Algorithm Has Changed Over Time