What are the rules of chanting the Gayatri mantra? Who are eligible to chant this mantra?

 Gayatri Pariwar in Haridwar published a book “Super Science of Gayatri”. Its Author Pandit Shriram Sharma Acharya is considered as a supreme authority of the Science in our times. I strongly recommend you to read. It is priced at Rs20 or even a pdf version should be available online.

I strongly recommend you to read.

He recommends to chant atleast 24 times in one sitting with one pointed concentration (on four level of speech).

Sai Baba of Puttaparthi suggests, Surabhi Mudra while performing Gayatri Sadhana.

https://www.google.com/amp/s/stylesatlife.com/articles/surabhi-mudra/