Theres a trick.
If you do trial exam after trial, and are not correcting or identifing the errors or concepts you are not 200% on, then they are useless, because the number or %age you are getting is just stuff you know. It's OBVIOUSLY stuff you are getting wrong you are not clear on .
A lot of people will read the solutions and understand their mistake, then move onto the next exam? It's very common, however that is useless aswell. Because after another 5 exams, they have forgotten their mistake! (So make sure you write down what you screwed in the trial on a seperate paper.)
What you should do, is take out 2 - 3 hours in the morning/afternoon, and go through your textbook. Have a scrap page next too you. Go through all the worked examples in the book. If some examples/ or some pages you see which has questions you don't understand, write the page number down. Then take a break, and after that, start hitting each page number you have listed, and work on them, to understand them, ask here, your teacher, friends etc.
By spending about 5 - 6 on that, you have IDENTIFIED ALL YOUR WEAK POINTS!
Make your bound reference around these key areas. The areas which your not sure upon.
After that, you will DEFINETLY do much better!