Fountain of Knowledge

Are there any hard, fast rules about how to transition scenes within a chapter? I've seen different methods. For instance, I seem to remember that when I was younger, reading Nancy Drew that if it was just a passage of time, there was an extra line break or two, but when the entire scene changed, there was a harder deliniator (like *** or something).

Comments about this are actually part of a lot of the feedback I get, I think I might not be doing it right, so I'm wondering if there is a 'right' way to do it.

On a simliar note, in dealing with two different points in time in the story. Say, now and then 1,000 years ago, what's the best way to indicate that the time frame has just shifted back and then forward again? I usually put something like

1,000 AD
fdaskfjdsl sfdjaldfkjo fdaskjlfasoeiur


***

Now
fsadfa dfadsfa adfdsj


Or somethign like that. But is that appropriate? Any other suggestions on how to do that?