Make sure everything is only seen by friends. And yeah, facebook does have a stupid thing where if you like something, it'll show up on your friend's timeline... or if you comment on something it'll show up on their news feed.
I used to see photos of other people's children because someone on my friend's list commented on it. like,
I just don't care
I have stopped using Facebook so much.. some of their "features" are really stupid. I don't want anybody to see what posts I like or comment on but there's no option to turn it off.