What steps should be taken before migrating to BSNL WI-FI Modem ?

If you are upgrading through the your ISP then you have no worries as their thecnicians are trained to troubleshoot this model of modem therefore you can ring and ask for help. If you are upgrading to a modem/router of your own choice then your ISp will not guarantee it will work nor do they guarantee they will be able to provide technical support. It is best to wait til you et the new equipment and read the manufacturers manual and the ISP instructin liflet. Good luck