One of the best instruments I found is the Emotion Matrix from Tenra Bansho Zero:
http://tenra-rpg.com/support.shtml
You roll on the table to give players the first impression for important NPCs (I found out it works for locations as well) when they first meet them.
It's just the impression, so the emotion may change as soon as they first interact, but it's been impressively entertaining until now.
GM and players can change the result bartering points that are used in the game for advancement and roll boosting, but it can easily be adapted.
Obviously, PC roll on that for each other's first impressions at the start of the game.