I use LinkedIn. My profile is up-to-date, and I open the app a few times a week (at least). I subscribe to some topics and groups and companies that interest me, and they feed me info relevant to my interests.
I don't Facebook or any other social media. I'm pretty much unfindable except through LinkedIn. I have not shared my address book with LinkedIn despite their many requests for me to do so. So none of my friends have been spammed to join up.
I'm a EE with a PhD, and I went to good schools. I've been out of school for 14 years, I work in development, and I'm fairly well-known in a small sub-section of an industry (through papers, conferences, government reviews, etc.). I've advanced rapidly through the technical ranks at my employer. I get shit done, and I'm very good at making things work. I'm a prize to the development folks, and my success has been based purely off of my technical capabilities. I have done well in making myself "indispensable" at my company (in that they'll lose years of knowledge when I leave).
Outside of the technical realm, my company is manager-heavy, and management is generally filled with weak, selfish, incapable, and insecure folks; it's a complete Dilbert universe. And these are the people who "manage" me, but they're not involved in my work assignments, and they're not involved in anything that I do for the company other than signing my time card and doling out my annual "performance" review. I've been through three managers in my 13 years with the company, and my managers have had four of their own managers in those same number of years. My "manager" has been junior to me for at least six years.
A couple of years ago, these asshats started trying to do some stupid, unethical shit and trying to force me to work for other stupid, unethical people who had done some pretty bad stuff. I refused (for good reason). It turned into a months-long shit storm with some idiot from HR and these asshats threatening to fire me dozens of times over; and I immediately invited them to go for it. They ultimately backed down; showing their hand (that I AM indispensable). And that's where LinkedIn comes into play.
Half my interviews (and offers) have been outside of my own efforts; they're from people finding me on LinkedIn based on my background and skill set. I fit a need for those looking for a "mid-career" or senior development guy who does what I do. There's also an option somewhere in there where you can turn on the "I'm looking for a job" and recruiters will know that you're on the hunt while your friends and whoever won't be able to see it (recruiters from your own company might be able to see it).