I have all 20 character slots occupied so I won't benefit from it but I think, considering that no class change token will ever be introduced, following introduction for new characters:
During this introduction the character is led through a story that allows him to test classes. FOR INSTANCE: To this end he gets a sort of magical scroll that temporarily gives access to class skills of a specific class and he can test these skills during a short combat. Then he can select another scroll to test another class.
At the end of the introduction he has to decide for a class.
Players who already know what classes they wanna chose can skip this and go straight to the class selection upon character creation.