Hi, CJ. Go to www2.fwi.com/~kruny/ for great information on crown molding. The best approach is to miter outside corners and to cope inside corners. All the directions to do that are shown.
You could check all the angles in your house and confirm that they are actually 90 degrees with a bevel gauge and protractor. This helps if your walls are not square. You only have to do this for outside corners. Coped inside corners will take quite a bit of angular misalignment without showing a problem.
You normally do not need to know the angle between the wall and the molding unless you are going to cut and install a backer strip of cut 2x4 to make installation of the crown easier. This is normally around 34 degrees but it can vary with the particular molding that you buy.