Question Premise: It is said in the scriptures and Bhagavad-Gita that people should do only the work assigned to them according to the chatur-varna, and that chatur-varna is according to karma and not birth.
Question: How can a person know in which varna he is included?
Answer by Romapada Swami :
Varna can be discerned by the qualities an individual possesses, and there are ample descriptions of these qualities found within the scriptures. Likewise, scripture also directs us to understand the finer points of application of these scriptural teachings by seeking guidance from a qualified spiritual preceptor. Based upon the qualities and tendency towards work and behavior that the individual exhibits, varna is determined.