I have been fairly disengaged from Facebook for a number of years now. I don't like the targeted advertising, the insistence that everyone in the world but me is playing "Candy Crush Saga," or the encouragement to complete my profile so that the world knows the size and location of every mole and birthmark on my body.
But LinkedIn is not Facebook. (Thank God.) It's a professional networking tool that can be one of the most effective resources for your lifelong career development. Notice that I don't call it a "job search" tool, because it's about cultivating an ongoing presence and set of connections, rather than a one-shot wonder.
Here's a great article, written with flippant panache, with the basic strategies you can use to make this resource work for you.