sir how should i prepare for entrance exams ,iit and jee main

dear arjun 
you need to do a proper planning for that , 
just start preparation as early as possible , and keep checking your progress everyday besis , 
and after 4-5 days , attane a mock test on the topics that u revised earlier . 
and attend a full length jee mock test in every month , 
and follow the right books , ( you can check askiitians blog for books ) , and u can even enroll to any test series , 
HOPE IT CLEARS 
REGARDS