One important thing is to avoid information overload. Unless it's relevant to the current session, it should simply not be present. If an NPC the characters met earlier will play a role in the session, then it should be in the DM's notes and possibly the players' recap as well. This does risk spoiling things a little, which is a problem I have with television shows (e.g. at the beginning of the show, during the recap, they show a character's brother who hasn't been relevant in 2 seasons, so you know that the brother is going to show up in this show...), but c'est la vie.
Agreed. It's why I only listed the four basic contact points. You only need a passing reference on most days, but players and GMs need the link if you are going to run sessions with rotating GMs in my own experience with the RPGA and table top.