Root rewarded England's selectors with a fantastic innings of 73 off 229 balls to help England to 330 all out, a score that seemed unlikely when he came to the crease on 119 for four on Thursday.
"It's not an easy pitch to score on and they set very, at times, defensive fields so you had to be very patient and be very selective of the areas you were going to score," the 21-year-old said at a press conference broadcast by Sky Sports News. "I just tried to wait and be as patient as possible and be really disciplined and grind it out."
Kevin Pietersen also contributed 73 on Thursday while Matt Prior and Graeme Swann added half-centuries to boost England's total.
They were firmly in the ascendancy at stumps when James Anderson's three wickets had reduced India to 87 for four.
"Kevin's knock was fantastic and so was Matty's, and Swanny's was very vital so we've got ourselves in a decent position," added Root.
"It was a great spell of bowling (from Anderson). He's been brilliant throughout the series as he has been for the last three years. Hopefully he can come out tomorrow and get a few more."