Steem has a rather steep learning curve and I find this to be a good thing, it discourages spammers and freeloaders. As for your question "when do we know you're a witness?" I'm already a witness, at the position 60.

I wrote a mega-post detailing many aspects of the Steemit platform, you can bookmark it and refer to it when you feel a little lost:

https://steemit.com/steemit/@dragosroua/the-7-fundamental-questions-about-steemit

Steem on!