(1) I found the Jupiter’s position if 1st, 2nd, 8th, 10th & 12th bhava in Main chart & even in D27 Chart very important in making one Guru.
(2) In my opinion it took many years to understand the concept of Jupiter and in this small post it is not possible to describe all.
(3) Atmkaarka concept propagated by Jamimi is actually from Brihit Prashara Hora Shaastra and this theory fails (1) In case of twin births (2) It is hardly impossible to predict from this theory (2) Annual horoscope (3) Horary Horoscopes. So two person having common horoscope, in case of twin with Aatmkaarka forming Guruyoga will make both of them Guru makes no sense.
(4) Guru, Kathavachak, preachers & Teachers comes under the influence of Jupiter depending on the strength of guru.
(5) Venus is the Guru of Rakshas but due to Rajsik nature of Venus as per Vedic Jyotish it will not be a Guru with satvik nature. Though in sky it shines brighter than Jupiter. So Venus can not replace Jupiter
(6) D20 chart, D27 chart & D5 charts along with Rashi Chart & Chalit Chakra are used to judge Guru yoga with spiritual power.
(7) Bollywood star Amitabh Bacchan from his famous KBC became like Guru he has powerful Venus in 8th with cancellation of debilitation replacing the position of Jupiter in 8th but again sorry to say he is not as Guru as texts on Vedic Jyotish permits.
(8) It is true definite position of Venus in any horoscope makes one Guru in the field of arts, music & up to certain extent literature too. But it is still far from the concept of true Guru.
(Follow link: https://www.facebook.com/notes/vishal-aksh/who-is-true-guru-deva-guru-brispati-or-asur-guru-shukaracharya-part-02/404687469689475 to view this post written by me on my facebook page)