Got my most recent job through LinkedIn. 2nd order contact found me in a search and my 1st order contact set up the interview.
I keep my LI profile as a superset of my resume. I keep it public, don't turn on the "looking for work" stuff, and NEVER look or write to the social feed.
One primary rule I never break: I only connect with people that I've worked with for at least six months. I'm not a job hopper, but spending a week onsite with a client doesn't make you best pals. But if you worked on a long-term project together, connect. HOWEVER, if that other person is one of those collectors that has 500+ connections, skip it.
I never apply to open jobs broadcasted to me. There's a steady stream of recruiters that contact me and I can one-click dismiss them. Not a lot of effort to do that and I'm not offended at reachouts. That lets me keep a pulse on the job market and salaries in my town.
It also lets me see which companies are bad news. When you see the same job come in from multiple recruiters over a few weeks, it's not hard to reverse-search the listing and figure out what's going on.