Short-cut
Ax-Man pretty much covered it. The best way is with a puller, but the redneck way usually works too (Guilty!): after you've removed the nut, take a rubber mallet and smack the flywheel right on the magnet side. After a few good smacks, most will fall right off. Personally, I haven't broken a flywheel yet doing this, but I guess there's always a first time!