Constitution, in general, would spread over the topics of Polity (Indian Constitution), Governance, Social Justice in the GS2 paper. As these topics are intertwined and have strong interconnections, I would explain how to study these topics for the GS2 paper. As the article is written explicitly from a Mains perspective, please note that the strategy for Prelims would be different.
For Polity (Indian Constitution), if you have prepared well for your Prelims, then it will be relatively easy as content from the Indian constitution plays a supportive role here. Direct questions about the Indian constitution are scarce. Since the answer for the paper requires the aspirant to substantiate with relevant articles from the constitution, this area will be easy if the effort has been put in during Prelims. Aspirants can refer to Laxmikanth or DD Basu for managing this part. If you have also referred to the bare act of the constitution during your Prelims preparation, it would further cement your basics. Please note that the time for Mains after the Prelims exam is less and hence, please make sure to manage these areas beforehand.
Coming to the Governance part, the aspirant has to understand that the questions are based on the application side of administration. Hence, the backbone to this part is the Polity/Indian Constitution, and the answers should have an external appearance with current affairs and relevant issues in the Indian administration. Hence, the material that an aspirant should refer to is Laxmikant/DD Basu/ Bare Act and an excellent current affairs magazine. If you have revised the current affairs magazine of your choosing regularly during the Prelims preparation, then the effort you have to put in will be reduced drastically. The catch here is to do critical and analytical thinking of government schemes, relevant current affairs, developments in polity, etc., and then apply what you have learned with the support of the static part of the constitution into the answers to handle the questions related to it.
In the case of Social Justice, what matters is that you understand the social context in India. For example, it includes vulnerable sections (SCs & STs, Minorities, Children, Women, Transgender, Elderly, etc.), social sector development (education, health, poverty, hunger, etc.), and welfare schemes related to these areas. Hence, not only should you know the basics of the Indian constitution and read the current affairs magazine regularly, but you should also follow an approach that is fundamentally strong and at the same time provide a real-world solution. Hence, you should put your thoughts and substantiate them with examples, data, etc. The need for these is critical in Governance and Social Justice. Therefore, there is a need to supplement your answer with the needed information. Kindly make sure that you pick up the required data, facts, reports, examples, figures from the current affairs magazine.
Please note that the GS2 paper for Mains is one where getting high marks is comparatively more rigid. Hence, one has to put enough effort and go through Previous Years’ question papers to understand the needs of the question. Kindly prepare on these lines and continuously revise your current affairs material that has good content. I wish you the very best for your Mains exam.