Content Marketing is always going to be one of your two best means of attracting attention / links.
Creating valuable tools is the other of your two foolproof strategies to earn valuable, natural links. Moz, Quora, Facebook, Twitter, Google, TwitPic, Flickr, etc. all earned their attention & links, mainly, through building useful tools.
In sum: create valuable content and online tools, you will earn natural and valuable links.
Of course, there are some techniques to amplify and/or speed up the bang for your buck:
- Networking. Develop a network of related, interesting, authoritative parties. This includes all social media marketing, meeting real people in person and talking to them, and building relationships with key bloggers/journalists that cover your industry (specifically, seek out the linkerati: the class of people that tend to share a lot of links online.)
- Controversy/Newsworthy Activity: Do something controversial, attract attention. Do something actually newsworthy, attract attention.
- Technical improvements: Canonicalize. Parallelize download requests. Minify. Structure pretty permalinks. Etc.