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?

Hi there.  :)
The manual4 gives you a ton of data to look for, but you may find the EPR settings on the sim plane to be a bit off then. However, the -500 ft/min approach would be a little to shallow when aiming for the standard 3.0 degrees.
You Vref (depending on the weight of course) is somewhere in the range of 130-140 kts and, in no wind conditions, you then should be more on 650-700 ft/min descents for example.

But here are more Vrefs, all from the manual4.
http://img217.imageshack.us/img217/2240/vref.jpg
If you take the rough method of looking at your groundspeed and setting your planned descent rate to x5 that value, you should be good to go on a 3 degree approach.
For easier calculations, you may also just take GS x10 and then divide the thing by 2.

So if your GS display shows some 160 kts on a heavier plane, 160 x10 / 2 = 800 ft/min are the desired rate. The green arc on the ND will also help you planning your approach. Set the field elevation in the MCP window and place that arc right in the runway.
On good charts, you will also find a small table to the lower left to show you some timing and descent rate values for certain groundspeeds.

Here's an example.
http://img850.imageshack.us/img850/3864/chartn.jpg