A lot you just find out from reading the boards, or from breaking one of the rules yourself.
Some you just find out by deductive reasoning.
TER also likes to make sudden policy changes  without saying anything.
As far as the Top 100 list, the rules are that a provider has to have a minimum of 20 reviews, and she has to have a recent review within the last three months. No, those aren't written anywhere (maybe in the TER admin manual, lol, but nowhere for us lowly members.