Link building has been important ever since Google burst on to the scene with the claim that counting the links to a site was the best way of rating its importance. Of course, this got abused horribly, and ever since there’s been a succession of new elements added to the algorithm – each predictably abused too. But links are still critical, and it continues to be the case that some links are more important than others.
This leads us to the next question: what do the best links look like? Most experts seem to agree that Google is looking for ‘natural’ links (those which might have built up without any effort on our part) …and that the search engine is very good at identifying what’s ‘natural’.
If it’s that good, you may well ask what the point of artificially encouraging links is, right? Well, think of it like following up on press releases. You could just send these out and put your feet up, but you’re more likely to get results if you prepare the ground beforehand and do some chasing afterwards. With links, you could wait for other sites to notice you and quote you with a link, but it’d be better to identify worthwhile candidates and draw it to their attention. Google is looking for what happens ‘naturally’, and with so many people out there chasing links, doing nothing is no longer ‘natural’.
The main aspect to ‘natural’ linking, however, is the relevance of the sites. You’ll be able to find all sorts of impenetrable academic papers out there describing how the web can be described in terms of multidimensional thematic neighbourhoods. What it boils down to though is that a great link is one from a site which primarily links to great sites in the same subject area.
One holy grail might be the surprisingly few independent trade and academic journals which have spent 25 years building up niche websites about their area of technology, which only link selectively to supplier sites as a reference in authoritative articles. If you’ve got one of those in your sector, work it for all it’s worth.
For much more on link building, try guides like this multi-part one from Moz.