your mid year exams should be in a similar format to the trials and final exams
depending on how much you've done you will be examined on
a) what is history
b) your case study
i found the best way to organise my notes and reading was as follows
WHAT IS HISTORY
Pick about 4 historians from the ones you have studied and make notes on them in terms of how they wrote history, what sources they used, what they thought of as the purpose of history and what their context was. with this information for each historian you should be able to handle almost any question they throw at you. Be compared to contrast directly the differences between these historians
CASE STUDY
Pick three historians or historical views of your case study and write your notes according to the areas covered in your case study. Eg. for winston churchill you would write notes on WWI, WWII, foreign policy etc. To check what areas are part of your case study check out the syllabus on the BOS site
Good luck!