Here is a video, showing how to skip the fire sequence in Nancy Drew: Message in a Haunted Mansion.
It looks like you have to do either the fire sequence or the séance sequence, in order to start a second conversation with Charlie. Otherwise, he tells Nancy that he's too busy to talk. Louis does the same thing. Does anyone know of a third way to get Louis/Charlie to talk to you? If there is a third thing which triggers a Charlie conversation, that could be a timesaver!
In small timesaver news, you can start the game by setting the clock to 7 AM and robbing Charlie. That way, you can talk to Rose and rob Charlie on the same trip, and you can talk to Abby and Charlie on the same trip. It's multitasking! It saves about five seconds.
In smaller timesaver news, I think it's slightly faster to double click when you enter Nancy's room, which zooms in on the dragon. Then back up. That puts you closer to Nancy's alarm clock then entering Nancy's room and turning right from there. The timing needs to be pretty exact, though, and it could be one of those navigation tricks which is too fast/tricky for human reaction times. I only discovered it by accident, myself!