how much % marks are necessary?
They put >60% in 10th, 10+2th and b.tech as their minimum reqirement but seriously it is not enough. Microsoft is one of the most top rated company. It will require minimum 80-85% to impress your interviewrs that you have the talent to work for this prestigious company and not to take you as lightly as the others.
There are still some exceptional cases but those are exceptional, you have to be a practical thinker.