Questions to answer: What version of InDesign? What file format are the pictures? How do the pictures look if printed directly from Photoshop? What kind of printer are you printing to?
I am using version CS5.5
Most of the pictures are saved as high quality JPEG or Photoshop. When I print to my lazer printer or my inkjet printer, from any program, the pictures turn out fine, but the printing company, er, whom I am assuming is using a printing press, the quality comes out just a little too dark. I am sure that I saw a setting to adjust this, but can't remember if it was within InDesign or if it was in the process of converting to PDF, which I am using the print quality setting, where I though I saw this adjustment.
ps.... thanks so much for helping, I am not an experienced InDesign user!
How do the images look in ID when you turn on Overprint Preview in the view menu? This is a much better preview of what you willl see on press.
InDesign doesn't directly support grayscale color spaces, so the gray values of your images are placed on the black plate in the current CMYK working space. Does your working space match the press conditions? If you haven't changed it, theres a good chance that your working space is set to SWOP Coated which would tend to look lighter with any given set of numbers than the output from a sheetfed press. It's also possible the printer is using too much ink.
What sort of document is this, and what kind of paper is it printed on?