Basically you have three kinds of statements if you categorize them by temporal reference:
Statements refer to the present: ego hoc facio = "I am doing this"
Statements refer to the past: ego hoc feci. = "I did this." AND ego hoc faciebam. = "I was doing this." AND ego hoc feceram. = "I had done this." All refer in different ways to the past.
Statements refer to the future: ego hoc faciam. = "I will do this."
Heres the rule: Always convert the time of the Main Verb to the Same Time of the infinitive. Always make the subject into the Accusative Case.
Present: ego hoc facio becomes dicit / dixit / dicet me hoc facere
Past: ego hoc feci. AND ego hoc faciebam. AND ego hoc feceram becomes dicit / dixit / dicet me hoc fecisse.
Future: ego hoc faciam. becomes dicit / dixit / dicet me hoc factur
