It's easy to read a book but it's very difficult to cram its lines as it is, read a page once normally and then again read it understanding the meaning of all its lines
Take a highlighter or a pencil and mark all the important points so that when you do revision you shoud not have to read the whole page again.
NCERT is just a brief introduction to the topic and usually you will find that in examination questions are asked more in a deep way. So, whenever you read NCERT make sure you also learn more about that topic from other sources.
Make short notes of every page of NCERT Book. SHORT-NOTES are the squeeze of things you understood from that page and read these SHORT-NOTES regularly so that you don't forget the old topics you have studied.
Students usually do not solve back exercises because they are confident that they have understood the chapter and need not to solve back exercises. (This is biggest mistake) Always solve NCERT back exercises, they are diificult and might also take some time to solve, but they will help you analyze how much you have learned from that chapter.