Dear Professor McGonagall,
How long does it take to learn how to become an animagus? How will I know what animal I will be?
Dear Future Animagus,
First, might I suggest that you sign your inquiries, so that I may assign House points to pupils who pose particularly pertinent queries.
As to your question, Animagus Transformation is covered in seventh year Transfiguration. I hope you have earned a sufficient grade on your Transfiguration O.W.L. to progress to advanced studies. Not all students are capable of the Animagus transformation, as a certain inherent talent for such self-transfiguration is necessary. Provided you have the requisite talent, dedicated study and practice of half a year is typically required for success. I am sure you can appreciate the dangers of attempting the transformation without sufficient preparation and supervision. Students have been known to become “stuck” halfway through the process, and, while becoming “unstuck” is possible, it is quite painful and traumatic, as Madam Pomfrey can attest.
You would rarely know in advance what animal you will transform into, should you be successful. The answer lies at least partially in your character, but may sometimes be divined through extensive self-knowledge. Few students have this level of insight into their character. Instead, the assumption of an animagus form is often enlightening and leads to, rather than proceeding from, self-knowledge.
I caution you against exploring this area without guidance. It is a rare witch or wizard, indeed, who can succeed without tutoring. Should you inadvertently transform prior to taking up formal study, please remember that you are required to register your animagus form with the Ministry of Magic. I assume I shall be seeing you in Transfiguration class come September first.
Hogwarts School of Witchcraft and Wizardry