I’m sure somone will post a link on how to install crown molding.
Genereally speaking, you don’t miter the corners cuz the angles become too complex–even to MEASURE accuately, much less cut. Since the molding does not sit COMPLETELY flush againt the wall, you start getting into the world of compound miters, and unless you really know what your doing, you’re better off going with the coping method.
Coping the corner joints makes for a tighter, better fit–though it can be a lttle tricky (at first) also.