A popular tactic before was to use something called a link wheel. The simplest example is with the picture here. Links are sent to the sites that link to each other and link to yours. Each site in the link wheel will only link to 1 other, and link to yours. This took advantage of being able to pass link juice around and around, artificially inflating the amount of link juice that was passed from page to page.
This was in 2010. Google realized what was going on and now sites that use this are heavily penalized. So why am I talking about this if it is old news? I still see people asking about it online, and I still see people wanting to buy them. I have even had people want me to make them. I can do it, it is not hard to do, I just refuse to do it because I will not be responsible for destroying someone’s site.
The example I gave in the first picture only shows the most basic of link wheel. They can get much more complicated, and that can make them more difficult to spot. What makes them easy to spot is that they usually form a closed loop. The last site will often link back to the first site in the wheel. Again it is easy to spot because this forms a funnel effect.
As these wheels get more and more complicated they can add on more tiers. They become quite a bit more difficult to manage, but like anything this big, it can result in a huge link juice boost. Again like most link wheels it funnels making it easy to detect. The world wide web is called this because websites link to other sites. Not just 1 or 2. Most websites will link to a number of different sites. So when the amount of websites goes from a large amount down to a fewer amount, and fewer amount, and ending in a dead end it is a big flag.
It is for this reason that most internet marketers will not use this model. Even with the open ended link wheel where the last does not link to the first, Google has become pretty good at spotting these and heavily penalizing domains that use them to rank.
So we know what does not work, what does? Most people now are using a milti tier pyramid model. The lowest quality sites at the bottom and your money site at the top. The lowest end will link to the tier above it and other general niche authority sites that do not compete with your money site. The tier above that will do the same, and eventually it gets to the money site where even the money site will link out to other sites. If you use enough authority sites to link out to, it removes the funnel effect while still letting you pass on quite a bit of link juice. I know this is an over simplification of how it works, I will cover it in more detail in a future posting and update this one with a link.