Specifically, from the Q&A, he says:
> Q. What is genius, and how is it produced?
>> A. Let us take several specimens of the species, and try to find some one thing common to all which is not found in other species.
> Q. Is there any such thing?
>> A. Yes: all geniuses have the habit of concentration of thought, and usually need long periods of solitude to acquire this habit. ...
His training system -- the A∴A∴ -- is designed to lead people to their genius. Interestingly, it is very similar to this checklist: it teaches self-discipline (by having to follow a specific training program); studying great people and works of philosophy, metaphysics, mathematics, etc; controlling emotions; controlling thought (including constraining it to a single idea); writing down ideas; etc.
I think Crowley goes much further and was more rigorous in his approach to applying the ideas listed. In his view, you don't _become_ a genius through this work, but connect to the genius that is already inside everyone. Connecting to this Genius and finding out your goals in life is the key to a joyful life -- or, as TFA says, 'Establishing a clear goal for your life should be a priority'.