You may have studied your material well and still not get the marks you deserve. Or you may have less work done and still maximize your results in the exam. What do you need to do to? Practice exactly what you have to do in the exam by doing as many exam questions as you can under the right conditions.
Assuming you are already working without any notes or text, timing yourself and learning how much you have to write as discussed earlier, then you are already on track.
What next?
Find out as much as you can about what is required in the exam questions. Pay attention to the action words in the questions. State, define, explain, give an outline, compare.....learn exactly what is required by these words. They will tell you how deep to go in your answers.
Too many exam entrants look for the content words in the question to see what it is about and then dump whatever they know on the page. It's better than nothing, but especially if you are well prepared, you will probably write too much and gain no marks at all for the extra parts you write!! It doesn't matter how much you know if the question doesn't ask about it!
Get to know your syllabus. Find out in each section the depth required. Don't rely too much on your text books - they contain a lot of extra information to help explain what you need to know or to make it more relevant or interesting. Make the most of your teacher's expertise.
Listen to your teachers and ask their advice. They will be delighted to see you thinking in such a proactive way about your own study progress and will save you a lot of time that you could waste trying to find out for yourself.