(i) Three or more words of the same parts of speech or phrases of similar
character should be separated by commas. For example:
Ram, Shyam, and Jadu went to school.
He came, saw, and went away.
Germany, Italy, and Japan formed an alliance.
(ii) Nouns or pronouns or phrases in apposition are separated by a comma.
Calcutta, the capital of West Bengal, has been renamed as Kolkata.
Ramesh, his brother, went to England.
(iii) Comma is used in between repeated words.
I will never, never do this again.
(iv) A comma is used after each pair of words or phrases joined by and.
The poor and the rich, the weak and the strong, the young and the old, have one Common Father.
(v) Before and after phrases and clauses used parenthetically:
Her son was, as it were, the apple of her eye.
The young man, I am glad to say, has escaped miraculously.