I'm still learning how the CDU and AP interact.  On my fourth flight from JFK to BOS, the CDU and AP finally got within reasonable distance to the airport.  As I didn't get ILS nav set, I tried to hand fly a visual approach.  If I recall there's no power settings in the manual.  I checked final approach speeds in CDU and tried to aim for -500 FPM with everything hanging out.  Wow, it's easy to get behind the 8 ball on this thing and you start porpoising like nuts trying to find right power and pitch.  I was able to eventually get it stable enough.

Any hints?