I would say that it's none of these and all of these at the same time.
The "best" backlink technique is one that maximizes relevance and minimizes questionable sources that engage in or allow questionable activity on their websites. The way to maximize relevance and minimize questionable activity depends on your trade.
In general terms, it's fair to say that there is no one backlink channel that will create miracles. Yes, you need a video channel of some sort, but the effectiveness of video marketing varies across different trades. Social bookmarking is an essential component. Blogging is a must, and so are articles.
Finally, an effective backlink strategy requires a system and consistency. Whatever channels you choose to pursue, there has to be a consistent trail of high quality submissions in order to get any results several weeks and months down the line. When accomplished properly, all of these channels synergistically come together to create the equivalent of "the snowball effect" in SEO.
