I use Firebug and IE Developer Toolbar all the time to debug tricky CSS problems. But occasionally, a tricky bug comes up that only appears when you go to print the page.>
In chrome developer tools (F12 \ Ctrl(cmd on mac) + Shift + C): In the emulation tab (From Chrome 32 onward IMHO), there is a tab for 'Media'.
There you can check the media emulation checkbox and select the media you would like to emulate ('print', 'screen' etc.)