The most important, and perhaps the most difficult, part of studying for nursing school is identifying the important information. It took me almost a whole year to get used to what exactly I need to look for in the textbook and other resources. It basically boils down to the nursing process, pathophysiology, and health promotion. Now you're probably saying "what the heck does that even mean, that doesn't help me at all" and you're right, it is a very general place to start, but the specifics take a little explaining.
What you're expected to know for any given test should be stated clearly somewhere in a unit outline or something along those lines.
So find it, and refer to it. This will tell you the topics you should look for in your book. Next, find those topics and mark them. For med/surg, often your topics focus around diseases/conditions or procedures. So what I do to organize the massive amount of information in any unit is make tables. Attractive, clean tables that organize information in an easy to read way. This takes some MS word skills and time, but the initial investment is worth it.
I make one, one-page table for each condition/procedure/etc. In my table I include a brief blurb in my own words describing the Pathophys of the condition. Then in a separate box, I list risk factors. I have another box for Assessment data expected with that condition - divided into objective and subjective data. Another box houses interventions, divided into pharmacologic and non-pharmacologic. Another box for Nursing Diagnosis and evaluation - most of which I try to do without a book, as sort of a critical thinking exercise - ask yourself "what sort of nursing problems does this problem create". Then when you are complete, print your table out so you can refer to it without your book and you have made yourself a neat reference for review before the test. It takes a lot of time, but just the act of finding the information and sorting it out this way impresses it onto your memory. Also, the table is a much easier place to find the info when reviewing for your exam. If I could attach a file, I would give you an example so you can see how I format it to fit onto one page for each topic.
This is a great way to gather, organize, and review information. I originally started doing this in my Pharmacology class, which was online, and it made a world of difference once I started. Try it. See if it helps.