What is considered canon in these forums? Eg.: Most of Indian mythology has been taught through word of mouth and stories from families handed down through the generations.
This answer is addressing the what is canon in Mythology or to be canonical, not suggesting that every answer would be supported by canon references.
To be a viable canon reference it would need to be a printed work relating to the subject. It can be a printed recounting of an oral tradition. This is following in the tradition of Wikipedias Verifiability policy.
While there are many oral traditions passed down in family and social groups, being passed down from one to one does not make an oral message canon. Being passed down from many to many (subjective, yep I know) implies a strong heritage for the message, suggests a possible oral canon tradition. But any only oral tradition would be difficult if not impossible to quantify in the format of this Q&A site.
To be canon on the Mythology site, the work must be published by a reliable source.