The campaign's tone, and its future, tangibly shifted with the advent of two events about a month into the game. First, Des very kindly purchased The Great Pendragon Campaign for me. Ah, the advantages of having your girlfriend as one of your players! Needless to say, the purchase of the GPC allowed me to really delve into the source material and have a structure upon which to hang the action.
LESSON ONE: Using the GPC has really showed me the importance of having a strong narrative outline in any sort of long-term campaign. This isn't an outline of plot, mind you, just an outline of what's going on in the world year to year. That way, you can have the events of the world occur and allow your characters to interact with that as they will.
There's a lot of good advice, enough of a taste of the arc to be entertaining without devolving into the dreaded boring character history, and a short paean to the joys of randomness:
Jim over at LotFP wrote in a recent post about how the current iterations of D&D have betrayed the game's sometimes random and deadly roots. I couldn't agree more. Knowing that your character could easily die from a bad roll simply adds drama and tension to the game. A recent example: Neilyn, a knight still at the top of his abilities, was ambushed by raiders while riding pursuit after a recent battle. He took a great spear to the armpit and nearly died. Just like that.
Alex, who was playing a Jewish mystic at the time, was able to heal Neilyn and bring him back from death's door--yet even that came down to dice rolling. Had the dice not cooperated, Neilyn might well have died. The drama and tension during that whole scene were palpable.
It's a long post, but it's certainly worth your time for the advice, insight, and inspiration.