Please elaborate how we can go about in this section since its the heart of any research paper. What are the expectations? What are the musts we should follow.
It depends on the topic or area you work in but in general, you should study a good amount of literature on the topic then compare the results of previous studies with your results and of course you need good reasoning to highlight the novelty of your work. Here are some articles that discuss this topic that you can turn to:
The guidance as per the following publications may further help:
Annesley, T. M. (2010) The discussion section: your closing argument, Clinical Chemistry, 56, 11, pp. 1671-1674.
Bagga, A. (2016) Discussion: the heart of the paper, Indian pediatrics, 53, 10, pp. 901-904.
Bavdekar, S. B. (2015) Writing the discussion section: Describing the significance of the study findings, Journal of the Association of Physicians of India, 63, 11, pp. 40-42.
Nair, P. K. R. and Nair, V. D. (2014) Organization of a Research Paper: The IMRAD Format, in Nair, P.K.R. and Nair, V.D. (eds.) Scientific Writing and Communication in Agriculture and Natural Resources. Switzerland: Springer International Publishing, pp. 13-25.
Perneger, T. V. and Hudelson, P. M. (2004) Editorial: Writing a research article - advice to beginners, International journal for quality in health care, 16, 3, pp. 191-192.
Şanli, Ö., Erdem, S. and Tefik, T. (2013) How to write a discussion section?, Turkish Journal of Urolog, 39, Supplement 1, pp. 20-24.
Van Damme, H. (2006) Editorial: Tips to improve the Discussion section in a scientific paper, Acta Chirurgica Belgica, 106, 5, pp. 479.