The process changes quite a bit as the season goes on, both in a positive and negative sense.  On the positive side, you begin to develop a relationship to your characters (the ones in your head, not the actors); they start talking to you, mouthing off, doing unexpected and unimaginable things.  And those are the moments you pray for, because the characters start contradicting themselves in the way flesh-and-blood people do.  On the downside, I think you can develop a degree of self-satisfaction and a sense that the whole world must know your characters as well as you do, and the narrative can begin to take on a kind of inside-baseball laziness.