Well, the best place to start is to speak to your teacher and ask him or her what precisely it is you need to revise for the specific exam you are taking. They are normally very good about this, so make sure you get everything you need to revise and to focus on.
Secondly, you need to remember as well that doing a multiple choice test can be a lot easier than the alternative. After all, you have the answers there in front of you. You just need to identify which one is correct. This can be a great bonus if you go through it carefully. The biggest strategy that can help you as you take your test is POE, or process of elimination. This is where you go through the answers one by one, crossing out the ones that are clearly incorrect, and leaving you with the correct one. Also, recognise as well that in most multiple choice selections of answers, you are going to have one absolutely bizarre one that you can quickly cross out, and then at least two that are going to look as if it is very close to the answer. You need to be aware of this and not get lured into selecting one of these for the answer.
Finally, as you are going through your revision notes, do anything to help you revise successfully. Revision is an intensely personal thing in my experience, and what will work for you will not work for others. So, be imaginative, and above all, own your notes. What I mean by that is draw silly pictures, use colours, come up with strange and bizarre ways of remembering facts and equations, walk around the room chanting them to a dance--whatever it takes you to do to learn them. And above all, good luck!
The question is what is your paper missing in terms of content? If your professor or teaching assistant has not been clear on this in his or her comments, do you know anyone in the class (or who took the class before) who received an A on these essays?
Have that student look over your paper and let you know what you are missing. A second set of eyes can prove very helpful when you have reached an impasse.
Take advantage of resources like study guides, textbooks and class notes. Google some key terms and with a little research you might find what points you have left out in your paper.