Thank you for addressing something for many new users of steemit. I am a new user, I read many of your introductory guides, yet I still made many of the mistakes you described here.
Trouble is, it is easy to make those mistakes when you start, but it is hard to undo. When I started, I randomly followed people, but the most annoying thing about it is that basically destroys your personal feed. It becomes filled up with junk useless content, and then the primary reason for using steemit (at least for me) which is reading quality content, is lost.
Now I have started to mute people, started to un-follow people, only a couple of weeks into it and it is already a tiring task. I decided, better do it now than later.