How do SEO agencies really, and I mean REALLY build links for clients websites?

Selected answers from the Dumb SEO Questions G+ community.

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  Rob Morgan: It will be interesting to know how SEO agencies really, and I mean REALLY build links for clients websites....
  
  How many agencies follow Googles webmaster guidelines to the word and how many air on the side of "manipulating PageRank"
  
  Surely if an SEO agency was to follow Google to the word, they would simply not get results for all their clients.
  
  Rob
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  Steven Ciccantelli: I have used a few SEO agencies/contractors and when I fulfilled my contract I have lost a majority of the links they created.So far I am not having any warnings from Google so I guess they did nothing wrong that WMT has found.
  The links that are left have little or no juice and I don't think that they did anything to help page rank.
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  Simon Fryer: Hi . That's a big question. Every agency is different, and a significant number of them are poor at SEO, but know enough to sell it and tie someone in to a contract. Similarly, there are some agencies out there. ; ;
  
  You've also got to take the level of investment in to account. Real linkbuilding, outreach & content marketing takes time, creativity, planning, and good execution. You're don't get that for the price of a hot dog. ;
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  Michael Baggelin: Link building is not SEO!!!, SEO is investing all semantic power into the Website structure and information architecture...
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  Simon Fryer: True  ;but like many things it has come to fall under the umbrella. ;
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  Steven Ciccantelli: Sorry I put link building under SEO umbrella.The one agency I used did charge me a fair price and wrote a fair amount of original relevant content.Being relatively new I tend to misuse terms and put them into wrong categories I guess.So doesn't link building help SEO in the long run?
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  Steven Ciccantelli: And heck I am sure there are awesome Seo companies out there.Perhaps because of my limited knowledge and budget I just was unlucky in my choices.
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  Simon Fryer: That tends to be the case . It can take a while to find a partner you're comfortable with. ;
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  Michael Baggelin: So I'm right but I'm wrong ;)
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  Guillaume Boucher B�langer: In every part of life it is!