One common SEO strategy that's been around since Google first began placing value on "linkbacks" has been the practive of building basic websites loaded with Search Engine Optimization keywords that link to each other in an effort to make the entire network of sites appear to be more authoratative and relevant to specific keywords with the intention of improving SERPS (Search Engine Results Page(S)).

The Search Engines caught on to this SEO trick and other techniques such as "link trading" quickly, and began giving higher precedence to sites receiving "one-way" links from other sites rather than for sites that simply linked to each other.

To get around this, some SEO experts have suggested setting up these networks so that each site only links to the main central site and one other site within the network (such that a "wheel" rather than a "web" is formed amongst the points in the network).  Typically, the main central site is the destination where final conversions of users into customers is achieved, and should be a professionally branded  site with your company and products clearly offered with optimized content used sparingly amongst otherwise targeted marketing copy.  Your linkwheel sites, on the otherhand, can be cheap, quick, and optimized for specific keyword phrases.

A common approach to build a linkwheel for your website is to setup single-page websites or blogs using free publication platforms such as WordPress, Blogger, and Tumblr, as these sites have unique IPs for each of your sites and you will benefit from their high PR rankings as they are already very established as authoritative sites by Google.  These "micro-sites" should be set up in the following manner:

• The chosen URL of your micro-site should contain SEO relevant keywords
• You should write a minimum 300 word article for each separate site; using unique content and keyword combinations
• Use your primary keyword phrase in the Title of your website - ideally in the first 7 words
• Use your primary keyword phrase in the FIRST PARAGRAPH of your article - ideally in the first 7 words
• Include 1 link to 1 other site in your linkwheel (this is important - do NOT make multiple links or your network will get flagged)
• Include 1 link to the primary conversion site in your linkwheel
• Make sure you do not copy content across your micro-sites or you will get delisted by Google

It is best to randomize your linking so you're not simply linking Site1-to-Site-2 and Site2-to-Site3, and so on; rather you should set up your linkwheel by linking Site1-to-Site5 and Site2-to-Site4 and so on.  If it seems as though this is complicated or too difficult for you to track, which is a good example of why search engines have a harder time shutting these rings down, then just focus on the 1 link to your primary site and worry about putting links between your other sites later or do them sparringly as appropriate.