I think what you need first is to think of your setup as one unit - your whole setup, from camera to computer/display to printer needs to be calibrated.
As I don't print anything significant at home, I just calibrate our computers/displays to fit our printing lab, WHCC using a colorimeter to make sure we're all on the same "page" first.
You have a few options here:
- Spend a few hundred dollars on a colorimeter package that will do display and print and calibrate your whole setup.
- Download a calibrated image and print it directly from the printer (if it has a card slot) and compare to other prints
- Try another printer (borrowed perhaps?) and compare prints
- Print an image directly from the camera (if it has a PictBridge USB connection) and compare prints
Can you perhaps post one of the "dark" images you're working on?