A too-strict attempt to apply the codified grammatical rules from a text-book can make translation into Latin more difficult than it need be.
FROM a Latin text the intention is (except in trivial cases) already there, and the translation should become obvious on reading. On the other hand, for putting a short phrase INTO Latin the actual context matters more than earlier answers/comments are allowing. This is evident from the emotional nuances which can be put into the English:
— I want to do this hoc facere volo
— I should like to do this hoc facere velim
— I am going to do this hoc faciam
— I shall do this faciam hoc
— Let him do what he wants faciat quicquid vult
— I shall do what I want faciam quod volo
— I shall do what I choose faciam quod voluero
— and so on.
In independent sentences the subjunctive in Latin can include shades of meaning to support the use of the would, could, might etc. of English. Other nuances may be indicated by word order as in, for instance, velim hoc facere, where the verb is strengthened by its position: I should certainly like to do this.
In the original question, facio quod volo is correctly and simply I do what I want. Quid me vis facere is a simple question, as in C. M. Weimer's comment: what do you want me to do?, which with a subjunctive becomes more polite quid me facere velis?, what would you like me to do?
Other possibilities and constructions are endless and depend on the circumstances, especially if the proposed action be included, e.g. what would you like me to have done? or is there something that you would like him to do?
As to the use of agere and facere, the former tends to mean get/have something done, or cause an action, whereas the latter more often implies something done by the subject.