There are two or three things you really want to do:
1. Calibrate your monitor. Start with Apple’s profile, but since color characteristics of all monitors change over time, you should create a new profile periodically. For best results get a calibration device, but you can eyeball it using the calibration tools in the System Prefs.
2. Install the profiles for your printer. Remember that these only work 100% if you’re using the manufacturer’s ink and paper. (There are devices that will produce profiles from any print sample. They aren’t cheap but there are services that will create the profile for you.)
3. Use the proofing options in Photoshop to preview the colors your printer will produce. If you’ve calibrated correctly and are using the correct printer profiles, you should be able to see a close representation onscreen, and adjust your colors accordingly.