At first decide your goal. Be consistent and dedicated towards your goal. If need be join some coaching institution, bit it entirely depends on your ability , if you are able to manage on your own then no need but if not then you should surely join one. Apart from this you must join some test series, you can also appear in some online test series , this a must to know your position and standing among others.

Next you must study for 6 to 8 hours minimum daily. It can extend to 12 to 14 on non working days.

Be thorough with your syllabus and try to memorize , understand and master each and every line of ncert.

Practice as much as possible.

Best wishes : )