Dear Aspirant,

Its good that you have already decided your destiny, to take admission in DTU you just need to clear JEE Mains with a good score and try to score more than 96 percentile for the safe side.

For that you just need to cover the every basic thing of NCERT which on taught on school and try to score more than 75% in your boards exam, besides you can also solve previous year question paper of JEE and try to collect the Coaching notes from big institutes of better knowledge ( it can be easily available), you can also take the help of online platforms like Physicswallah for Physics and many IITians are teaching in youtube, take their guidance as well.

But if you choose to take admission in coaching institutes from 11th then sure you can take it, there in many good coaching in Delhi also but I'll suggest you to go Kota ( Rajasthan) as it provides the better environment for the preparation, there they will guide you for each and every thing, but don't forget to solve the NCERT problems because it is the key to go to the Big Colleges.

For online programs you can take help of Unacademy and youtube for free courses.

Best Of Luck!!!