If you want to use facebook to communicate with friends, but dont like wasting time, just adblock the news feed. The first time seeing an empty newsfeed and not being able to scroll is quite an interesting feeling.
I just started hiding 'non-essential' people from my news feed when I saw a post pop up by them. Within about a week I was down to just a small core group of people I actually care about, and generally if I scroll down more than a page I'm met with a "Sorry, there are no more posts" message. It's a good way to keep up with close friends while filtering out the noise that wastes so much time.
I have disabled all notifications from Facebook. I find myself not visiting Facebook that often anymore.
This is fantastic. So much more useful than your average site blocker because it actually lets me get to the (admittedly rare) important notifications on Facebook while preventing me from wasting extra time.