Kaelaria is right.
Before I finally shelled out for a colorimeter, I must have spent two or three times its price in wasted ink and paper making unsatisfactory prints.
However, if you insist on trying to get things a little better without a properly profiled monitor, you might want to try the following just to see how close you can come (No guarantees!!!):
1. Download a good color printer test file, such as the one from Digital Dog's site (Andrew Rodney):
http://www.digitaldog.net/tips/index.shtml2. Make the best print of it you can.
3. Load the file into Photoshop, turn on "soft proofing", and diddle with the monitor controls until one of two things happens ---
(1) You get the image on your monitor to match the test print well enough, or
(2) You give up in disgust and borrow the money you need to get a good monitor calibration system.
Good luck!