Question: How does one ordain in the Pure Land tradition?
Response: I can only speak for how I became a nun but I believe it is fairly representative. After deciding that everyday life was becoming less important while dedicating myself full-time to Buddhism had become very important to me, I asked my Teacher, Ven. Master Chin Kung, if he would accept me as a nun. This was done through a translator who was at the Dallas Buddhist Association (DBA), where I was practicing and studying. She faxed Teacher, and he faxed back that I should "get ready."
It was arranged that I would spend the next year dividing my time between living at my home and living at the DBA. As the year was ending, I gave away all my possessions and prepared to move into a nun's dormitory at the DBA. I and nine others were shaved by Teacher who had come in from Taiwan for the tonsure and related ceremonies.
In 1997, the ten of us and some other monastics who had been shaved by Teacher but not yet been ordained went to Kaohsiung in Taiwan for the ordination training and ensuing ceremonies. About 600 monks and nuns studied and practiced for thirty-two days and at the end of the time were ordained in a ceremony that lasted many hours.
As you can see, becoming a monastic was a two-step process: first the tonsure and then the period of training that culminates in the Ordination Ceremony.