I tend to isolate myself at home late at night with ear plugs in, and I read and re read the passages over and over, then I pick out possible questions, and write them down.
I also highlight important prompt words, and quiz myself, until I can virtually see the text on the page with the book closed.
To write and understand what you have written, I know it sounds strange, but there have been times that what we write from text books or online sources, especially if done mechanically, does not make as much sense when read back.
Get the subject matter settled in your head, but dont cram for more than twenty minutes without taking a break, just a simple walk around the house whilst thinking of what you have studied lets it settle in, then go back for the next bit, break the subject down into "bite sized chuncks" and in doing this you also imprint the knowledge into your brain.
Above all dont panic or stay up too late trying to force it in, a couple of hours per night in the week preceeding, is enough if you are running up to an exam.
And a strange thing I have found over the years, read something totally different before going to sleep, something light and non related, (eg) a fiction story, it settles your mind.