I detest the overwhelming emphasis that is search.
So please do not take the following as applying only to SEs or SEO; link building is NOT, has NEVER been that limited, only SEOs and many/most webdevs wear such self inflicted artificial blinders.
The following is a cross post from a thread, The Foundation of a Link Building Project: Things a Business Must Know Before Starting, at WebmasterWorld. I liked my post so much I am 'content marketing' it:
I agree with just about everyone above, at least somewhat.
Disclaimer: yes, I have bought links, but not for years; yes, I have asked for links, but not for years; in both instances they were specific links for specific purposes.
You should have:
1. a really really good website.
Such that when compared with it's main competitors it pops. If it looks like everyone else's simply having better copy, even images/vids won't be enough for most visitors: it looks the same, it is the same. And also have the better/best copy/images/vids et al.
Note: why does Apple strive for the best packaging in the computer (just about any) industry, mmm?
2. link quality (authority, relevance, trust (ART))
As we have no knowledge how a SE applies or flows link values we can only use our personal judgement, asking:
1. do I believe the page/site has ART in my (or associated) niche?
2. do I believe that a link from there has the potential to inform their visitors that I too have ART?
3. do I believe that traffic through a link there is pre-qualifying the traffic it refers?
4. do I believe that a link there will refer n-traffic?
Note: how many of you consider back links as affiliate links?
I definitely prefer links that send traffic.
Note: as Google search traffic is just about the worst converting traffic on the web it is just not the diversification principle that drives my efforts for other referrers. However, as Shepard mentioned, if you build for traffic you get Google (and other SEs) at no additional effort/cost.
As robzilla mentions, albeit primarily as SE/Google bait, there are worthy links that don't necessarily send traffic. Many serious niche academics and thought leaders' sites send no to little traffic for the simple reason that their writings, while foundational, are not easy and so not popular.
However, I love to get their links for testimonial reasons and highlight them as such. And of course, I link back to specific works as appropriate citations/quotes. And where feasible I publish interviews, which offer all sorts of crosslinking possibilities.
Note: how many of you consider back links as testimonials?
3. Marketing includes link building includes site architecture
I agree wholeheartedly with buckworks:
I consider just about all my promotions to be part of my link building strategy, because people can only link to your site if they know it exists.
While few would consider site architecture, navigation, and URL design in the same breath as marketing buckworks' canonical observation is spot on:
People making links often just grab whatever is showing in the address bar, so make that as consistent as you possibly can so fewer variant URLs get into circulation.
Also give thought to future-proofing. Try to structure your URLs so they won't ever need to change. If you ever do need to change URLs, be sure to set up appropriate redirects, don't just leave the old URLs to break.
Note: rel=canonical is a bandaid not a best practice.
When looking at a link 'out there' also look at the page (and where on the page) it lands the visitor. Then considering the page topic from whence came and the page now on are subsequent (on page) links in a logical sequence? Are the potential in-site click tracks appropriate?
It's not just the link you acquire but the extant links once the visitor is acquired, not just the landing page content but that of the referring page and subsequent site pages. Is there a smooth flow or is the visitor buffeted/distracted?
And always always keep in mind your business purpose and the needs of the visitor. You went to the trouble of getting the link for resulting traffic (be it direct or SE) so don't drop the ball and the visitor once you've got them.
4. Marketing includes link building includes social interaction
Most businesses believe that to use social media they must have a formal presence, i.e. a FB business page, and then, given the dialled down (from ~18% to ~1%) natural sharing, buy ads. Which is good for FB.
I prefer to identify unexpected (as in non-obvious non-mercenary) SM influencers and then encourage them to share what they find worthwhile. Word of mouth, except for the rare viral tsunami, a modest slow growth endeavour but the traffic is eminently pre-qualified and motivated. It is social so keep it low key, keep it personal but by all means do try leverage wherever it seems appropriate. Likes are crap, shares are good, links are better, shares with links are best. Rinse and repeat for targeted platforms.
Note: I find that my app uptake by SM referred repeat visitors is many times that of normal repeat visitors.
Finally as Shepard says:
I've really started to think of link building as a "business development" area, even bordering on "outside sales".
Link building is customer acquisition is marketing is business development is serious stuff whether done indirectly via 'natural' unsolicited links or directly via solicitation. At least it is if you are in for the long haul.