Hi Nidhi,
Although I enjoy drawing and painting, I do not consider myself an illustrator, so I apologize if this advice is too basic for where you are at, but this is something helped me refresh my high school art class skills:
I went to the library and took out four different books about drawing and read them all, one after another, in a short period of time. I did some of the exercises on a newsprint drawing pad, especially in the early chapters of the first book, but mostly I just read. The great thing about reading four drawing books in a row was that where one book's description was lacking, the other books could fill in the gaps. And if I saw a tip or exercise repeated in three or four of the books, I felt more confidence that that information was important/credible. By the third and fourth book I was mostly skimming because I was largely seeing the same material I had already read, but I would still find new nuggets of information, or a new way of explaining something that helped. Looking through four drawing books in a row like that has helped me feel that I have a better understanding of what I am doing, or trying to do, when I draw.
I have also enjoyed these books in particular:
Watercolor for the Absolute Beginner by Mark and Mary Willenbrink and
The Art of Colored Pencil Drawing by Cynthia Knox et al.
Finally, I found Raina Telgemeier's page on "How a Graphic Novel is Born (and Raised)" (
http://goraina.com/2013/08/how-a-graphic-novel-is-born-and-raised/) to be very informative. She shows the stages she goes through in drawing a scene.
Hope this helps, and hope you have fun drawing :-)
Lisa