It works like this: 1. Realize that most of the world is out to distract you. 2. Realize that part of the way to do this is to make distraction, and access to distraction, as easy as possible. 3. Actively set up "friction" to reduce that ease.
In practice: I don't install FB on my phone; I have to use the crappier web version. I block reddit on my laptop, so I have to use my phone. Just by making stuff not ubiquitous, you add a little mental friction to using it that dissuades it usage.
One more: I always log out of FB and any other "easy-to-use" distractions. The act of logging in is costly enough (given my long passwords) that even if I open up the tab, I'll bail because I'm too lazy.