Best way to create natural backlinks?

[Netrunner]

Generic answers would be :

1. Create high quality content
2. Buy backlinks from trusted sellers
3. Backlinks exchange with fellow site owners in the same niche as yourself
4. Ninjalinking
5. Press endorsement, etc...

But, the truth is that these methods no longer drive SEO juice power like in the past. I'm not saying it's useless, but people over-spammed these techniques to the point that Google doesn't give them that much importance. If you manage to get a few backlinks from high authority sites, it will benefit you more than running after outdated methods. That being said, I watched a vid a few months ago in which a SEO Expert was talking about a link he bought for several hundreds, but nothing happened in the end... His site didn't get the push he was expecting, even though the seller had a powerful site.

Does Google know if you buy a link ?
Does high authoritive sites like that one became blacklisted because they got busted by Google for monetizing links and hence, lost power ?

I don't know, but I'm sure of something though. Backlinking strategies that actually work are not easily/no longer shared  . Trends in SEO don't have a great lifespan after all. Once a working technique becomes known worldwide, it's over. Google will just adjust it's algorithm and we'll get back to square one.