If you are preparing for an exam the day before, it is assumed that you know at least something about it, you cannot practically consider learning everything from scratch just one day prior to the exam. If you are down with the basics and have something to build on, you might actually have a chance of passing.
The first thing you need to do is focus on the actual exam that is coming up. It may be followed by other exams but if you keep thinking about all of them you will not be able to focus on any one. See all these exams as steps you need to climb one at a time and look forward only to the next step.
You need to look at the syllabus for the exam before you start studying. Most exams have a set format, where your knowledge from a specific area or chapters is being tested. Until you know what you will be asked, you cannot expect to prepare to answer.
Once you have the syllabus, start dividing it into chunks. Separate the topics or chapters according to their difficulty or length. If you know some of the chapters, mark them as easy and write them down in a separate list. Likewise, list the difficult or lengthy chapters separately so you know what you are dealing with.
If you have access to past papers, make sure you go through the previously asked questions to observe the trends and the type of questions you need to prepare for. This will also help you in selecting the topics or chapters which are important and must be covered.
Start reading the tough topics first and use a pencil to mark things and underline important words. Don’t try to memorize everything because you will not have time for it all. The best you can do is cover the tough chapters first and then come on to the easy ones in the end. Once you are done with all, you should sleep for a few hours and try to wake up early the next morning for revision.