The following rules, to be strictly adhered to by a Vedic Astrologer, are taken from Daivajñadharmopakāram (दैवज्ञधर्मोपकारम्) from Upakārasāhasri (उपकारसाहस्रि).
My beloved father and guru, Brahmasree N. Kameswaran, was an exceptional practitioner of Skandahora. Skandahora is considered the first and most voluminous scripture on Vedic Astrology. He reproduced Upakārasāhasri from palm leaves written in ancient Malayalam script to the present day script. This scripture is not published yet.
Skanda: Agastya! There are 24 rules that a daivajña needs to adhere to. I will explain them to you.