Hi Siva
SAP provides some Best Practice documents to follow across all modules and systems . Please see the following link which contains the Link to the Best Practice Documents in the Marketplace.
https://help.sap.com/bestpractices
Regarding your systems , to start off , please check and analyze the EWA reports in your PROD environments.
They provide a very holistic view of the systems and potential areas which might need changes like SAP Parameters , Database Parameters , Standard Background Jobs , Hardware capacity etc.
Hope it helps.
Thanks
Rishi