What are good ways to cite self-directed personal skill courses, such as improving memory, time-management, grammar improvement and sales courses on a resumé.
What category should these be listed under?
If these courses are generic, and the learnings from them are the general expectation for your role you are applying for, I would advice not listing them directly as it creates fluff in the resume and the hiring manager may end up missing other important details.
Instead, you can use keywords from the courses in your objective statement, and at other places within the details of the work experience you have for various jobs.
However if the courses are specialized, and is something that is either a pre-requisite or is above the general expectation of the role, then it would make sense to include them in your educational qualifications section, and optionally in the objective statement as well.
This could be the case for industry certifications (PSM, PMP, CISO, ITIL, etc), MOOC courses that you have done online (and have certificates for), executive education courses done at universities / b-schools.