Acing an exam is not as difficult as most people believe. It all boils down to the preparation. You need to practice, practice, practice if you want to ace your exam. Depending on the class(es) you are taking, preparation may mean many different things.
Let me give you a personal example. I'm taking this class in Business Statistics and I just recently had a big Midterm exam that was worth about 20% of the final grade. I aced it. I did not cram the night before the exam. Here's what I did instead: I prepared slowly but surely throughout the semester by staying on top of things for that class.
I did the assigned readings. I did some practice problems for the class too. I watched the tutorials. Basically, I prepared as well as I could for the exam. Also, another trick is that I asked a lot of questions and I asked for help.
When the Midterm was coming up, I had very little work and preparation left to do because I was on top of things throughout the whole semester. I wasn't stressed out about my exam. I didn't worry. Ok, maybe a little bit but preparing throughout the semester made me confident in my ability to ace the exam and I did!
In summary, the first step to acing your exam is to believe you can do it. Also, you have to make this your goal. You need to make school a priority otherwise you will end up slacking. This means no more playing video games 3 hours a day. No more watching TV 6 hours a day, etcetera...
Truth be told, it really is that simple. Give my tips and tricks a try and let me know how they work out for you!