Some agencies still focus on link building, but I’m unsure I’d call a strategy. The best link-focused agencies normally have a bag of tactics/tricks they love. These tactics are proprietary, which implies it’s difficult to find every one of them spelled out on Quora.
Having said that, there are several great tactics shared on regularly, and you’ll find a lot of interesting stuff exploring on that site too (lots of which is free).
However, so far as a technique, quality link building services plays second fiddle. Links aren’t the be-all-end-all of internet marketing – you need them to reach your goals, however, you also need a good social media presence, good content, website that converts, etc.
In my opinion, link building fits into a greater online content and PR strategy.
At my agency, we focus on a distinct segment (auto parts), which permits us to both cultivate content expertise (all my content creators are car nerds) and cultivate relationships with industry media (I’ve got a decent list of automotive journalists and bloggers I can reach out to and expect a response). Our strategy:
Create content hopefully auto enthusiasts will enjoy (and we of car nerds makes us somewhat successful at this)
Contact the best journalists/bloggers inside the automotive niche (whom we all know, or otherwise know via email) and “pitch” them our content
If/when the content resonates with all the blogger/journalist, we have a reference to the client’s manufacturer, and typically the link
The hyperlinks are editorial and range from top quality sites, so we have absolutely nothing to fear from your efforts. It’s 100% “white hat,” which you can’t always say about link building. The manufacturer name mentions put our clients in front of thousands (or tens of thousands) of automotive enthusiasts. I don’t really know 40dexppky the ROI on these mentions is, but it really can’t be bad.
…Not to mention, we’ve got a cool piece of content on the client’s site that may generate search and social websites traffic/interest for many years.
Our “trick” is an industry and niche focus. It’s difficult to create content that basically “pops” if you don’t have expertise in-house, not to mention that it’s difficult to find out who the top bloggers and journalists have been in a distinct segment without having done some operate in that niche for a long time.