An aspirant to the appreciation of Hindustani music will generally start with two questions in his mind: What is a Raga? And, how do I differentiate one Raga from another?
What is a Raga? A renowned music critic once observed that writing about music was as useful as dancing about architecture. So, critics and musicologists have their limitations as cultivators of public taste. There are as many definitions of the Raga as there are authors on the subject. None of them is a substitute for direct encounters with Raga-ness.
How do I differentiate one Raga from another? Once a listener gets a reasonable grip on what a Raga is, the differentiation of one Raga from another becomes possible through exposures to multiple Ragas.
The first step, then: Take any one Raga. Start with a simple Raga, like Malkauns. Go out and get ten recordings of the Raga by ten different musicians performing the same Raga, preferably in different genres. A few in Khayal vocalism. A few in instrumental music. A few in Dhrupad or Dhamar. Listen to each recording several times. Your musical mind will begin to identify what is common to all the recordings. And that, which is common to all of them, is the Raga-ness of Malkauns.
Second step: Now, take another Raga, an allied Raga like Chandrakauns. In this Raga, you could find Khayal, instrumental, Dhrupad, and even Ghazal recordings. Repeat the same procedure as followed for Malkauns. Your musical mind will now identify the Raga-ness of Chandrakauns. In addition, it will tell you how the Raga-ness of Malkauns differs from that of Chandrakauns. These differentiators are what constitutes the Raga-ness of Ragas.
If such a procedure is repeated across several Raga-s – whether purposively or otherwise -- your musical mind will also identify the dimensions of Raga-ness: the various attributes by which Raga-s are distinguished from one another. And, from this point on, you have taken an important step towards becoming a connoisseur.