Anyway, one more mandatory house rule that I've come up with, and been extremely happy with is the character background exercise that we do as part of chargen. I can't take credit for inventing this idea (it comes from the FATE SRD, and the Spirit of the Century roleplaying game, for those interested) but, as always, I put a bit of my own spin on it.
As soon as your character is finished mechanically, write a small blurb; no more than a paragraph or so, about an adventure of some kind that happened to him in the past. Every character will do this. Make three copies; one for yourself, and two that you fold up and put in a cup or hat or other container.
Every player will draw two character's backstories out of the cup (or hat or whatever.) If you get your own character, or the same character twice, but them back until you have two other characters. Read their past adventure blurbs.
Then, write a sentence or two about how your character was involved in these other characters' adventures.
Every player shares the adventures he has with the entire group. The purpose of this is to create a web of interconnectedness, past history, and relationships between the various characters, and you've got a strong footing right off the bat to start a campaign and explain why your group is all in this together. It also gives a lot of roleplaying opportunities that have proven out as great fun in playtests.