Inbound links and their anchor text are the second most important factor in SEO after the title element. Certainly in terms of the time involved inbound links will be the area where most of your effort in SEO will be expended.
There are five main aspects to consider when obtaining inbound links:

• The anchor text
• The linking page (the page on which the link is situated)
• The linking site (the site which contains the page the link is on)
• The linked page (the page on your site that is linked to)
• Acquisition or link building (how to get them)

The anchor text.
The anchor text is the text that users will click on to reach your site and appears like this in the html of the linked page:
<a href=”http://www.yourdomain.com”>This is the anchor text</a>
and on that page it will look like this:
This is the anchor text.
It is essential that the anchor text should contain the keywords that you have optimized the linked page for, in various combinations. If we take the example used in the Title Element post where our keywords were store fixtures, store display, retail display, retail fixtures, store displays, retail displays then these would be used in the anchor text of links to that page as well as the full title Retail Store Fixtures and Retail Store Display Supplies. The idea is to avoid exactly the same anchor text for every inbound link but also to ensure that every link contains either your title or keywords.
The linking page.
To paraphrase Napoleon in George Orwell’s Animal Farm “All links are equal, but some links are more equal than others”. We shall refer to the ‘strength’ of a link (strong link, weak link) although there are a number of equivalent terms used elsewhere such as ‘importance’ , ‘power’ and ‘value’. Factors relating to the page on which the link is placed which influence the strength of a link (apart from the anchor text) are:
The text directly surrounding the link. This is particularly true for links embedded in content but for those that occur outside the main content area, as in lists of links, it would include the description about the linked to site (page).
The text on the page. If the text on the linking page is semantically or topically related then the strength of the link is greater. For example a link from a page on the topic of antique furniture to your site on camping equipment would be a weak link.
Inbound links to the page. If the page on which the link occurs is itself linked to by strong links then in general links on that page will be strong.
The total number of links on the page. For any one page the fewer links there are on that page the stronger the links.
The linking site.
Inbound links are such an important aspect to ranking high in the SERPs that site owners are tempted into using any means possible to obtain them. Google says in their Webmaster Guidelines “Don’t participate in link schemes designed to increase your site’s ranking or PageRank”. They really do mean it and quite correctly refer to abusers as ‘spammers’ who are diluting the quality of their search results. Algorithmic spam detection has been implemented by all the popular search engines and improves day by day.

If you are interested in some of the detection techniques that might be used here is an introductory reading list; Link Spam Detection Based on Mass Estimation, Link Spam Alliances, Pagerank Increase under Different Collusion Topologies, SpamRank – Fully Automatic Link Spam Detection.

Collusion does not always involve a third party and you should avoid cross linking your own sites unless you have taken the precaution of placing them on separate Class C IPs with different domain registration information.
As the search engines become better and better at spam detection the bottom line is to avoid obtaining links from networks of colluding sites or participating in linking schemes of any kind. At best the links will be of little or no value and at worst your site could suffer an outright ban.
The linked page.
The linked to page should contain text that is semantically or topically related to the linking page. For example a link from a page on the topic of antique furniture to a page on your site about the wholesale stripping of Amazon forests would be meaningless unless you included a body of text that related the wood used in the furniture to the wood in the Amazon forest.
Acquisition or link building.
With all these constraints you may be wondering how you are ever going to find the sites which will provide you with strong links? There are two aspects to this question, how to identify the sites and then having done that how to persuade the site owner to link to your site. Link building is a lengthy subject and I shall cover it in more depth at a later date but a general approach may be as follows:
Identifying candidate sites. Finding the strong links that your competitors have obtained is a good place to start. Record the top 10 or 20 sites in the SERPs for your keywords and then list the inbound links to those sites. Then identify the common sites linking to them and those sites that link most frequently will be some of the strongest links. Most professional SEOs have proprietary software to do this kind of analysis for them but you can do it manually if you are methodical and spend sufficient time.
Let’s say for example that the keyphrase for which you are seeking inbound links is store fixtures. Google store fixtures and record all the sites in the first page of the SERPs. The first site is www.nasfm.org. Now enter linkdomain:nasfm.org -site:nasfm.org into Yahoo Search (we are using Yahoo search here because the Google link: operator only shows a sample of the links that it knows about). This will give you a list of all the inbound links that Yahoo knows about for the site. These will all be possible candidates for linking to you but won’t tell you which the important ones are. If you repeat the process for all the sites on the first page of the SERPs and transfer the results to columns in an Excel spreadsheet you could perhaps write a macro to determine those links which are most common to all the sites. The sites that link to two or more of your competitors are the important ones.
Obtaining the link. This is also a time consuming process and it is tempting to send a template email requesting a link to the site owner or webmaster. Resist the temptation because invariably 99.9% of such emails are never looked at or even considered. The best approach is to communicate by telephone in a very friendly way or to send a personalized email. Whichever you choose your success rate will depend on how much planning and effort you put into the communication and of course the links you require the most are the ones where you should put the maximum effort.