To train for a cero, you must be taught how to preform that cero by the creator. YOU must have no less that 100 sentences and 20 posts to learn the Cero. The creator can have as may sentences and posts as he wants. The creator also decides WHEN you have mastered the cero, however the maximum number of posts is 40 that they can make you train with it to.
-Bleach New Edge Staff