While quality content is nice, I actually disagree with the "write it and they will come" approach. Lots of bloggers write great posts in obscurity because they don't explicitly work on the SEO component. Great content is only great for SEO if you take a lot of steps to promote it and use it to get links.
Of course, great content make all your link building efforts better since people would rather link to a quality site. But it's definitely only step one.
To answer the original question, here are a few:
*Press releases
*Directory submissions to the top general directories and to the best, highly related niche directories
*Have an active social media campaign, including G+, Twitter, Facebook, Pinterest, and any other major platforms. Some of these provide links themselves, others are good for promoting that great content.
*Find sites likely to link to you based on co-citation research, and then send them direct, well crafted link requests.
*Guest blogging on relevant blogs
*Write great content and link bait and then promote it like crazy.