We can't validate the study materials of any other coaching Institutes. To be prepared for the exam you must need to follow the best books-

• NID DAT book by R.S. Aggarwal (aptitude section)
• Design drawing by Francis D.K.Ching
• Basic Rendering from Robert W.Gill.

Give mock tests, try to solve previous year exam papers by own your. This will boost your preparation. This test will determine your ability to think and create, how much genuine your thinking is. You can surely take help from various websites and applications but you're instructed not to copy them. You'll judged on your imaginary and creative skills. Practicing with these enhance your thinking ability, makes you more creative. There are various way one can learn from the internet or from the YouTube channels. Check out this link for preparation tips for NID DAT. http://design.careers360.com/articles/how-crack-nid-dat