[Courtesy of Brian McCue mccue.zoo "at" worldnet.att.net, December 1999]
A proper spin entry is one in which the stall break and rotation begin simultaneously. It is not a stall followed by a spin.
At the onset of the stall, the application of rudder causes the inside wing to stall due to a further loss of airspeed while the outside wing is not stalled due to an increase in airspeed resulting in the characteristic autorotation. If you are not careful and apply the rudder too soon or apply aileron too soon you get an accelerated entry (snap roll) and a wingover-like manuever (a zero). Apply too late and the airplane bobs up and down trying to fall off on a wing until allowed or forced to enter a spin (quite an ugly entry).
I have also seen straight ahead stalls followed by push to vertical, then snap roll and this was called a spin (also a zero). You are also right in that you are likely to find many judges mistaken and disagreeing on what is proper. My airplane is set up so that in level, decelerating power off flight, when the elevator stick hits the up stop the stall occurs and the immediate application of just rudder results in a very nice consistent spin entry. After the initial break, I add aileron in the same direction which speeds rotation and also allows a quicker recovery upon release of controls.