Try this, I did and it worked pretty well.
Step 1: Make a list of the subjects, the hardest and the top, the easiest at the bottom..
Step 2: For each subject make a list of the chapters and write how many pages are they..
Step 3: Start with the hardest subject and the hardest chapter of that subject..
Step 4: Write the important notes from the chapter, in your notebook or papers..(I bought a big pack of lined papers like the one they give you in the exams and I am working on these)
Step 5: For this step you should already be done writing the notes of all chapters, so now you print past papers and start working in them(for better results,do the past papers in exam conditions).
Step 6: After each past paper you finish look up the mark scheme and mark it for yourself(be mean with the marking).
Step 7: You will normally find mistakes while marking your papers, go back to your notes and study the chapter again(teachers assistance is also a pretty good idea).
Step 8: Thank me with a nice gift for accomplishing your target.
T.P: I bet you will say to yourself,"Oh man, but this is too much to do, and i don't think i have much time."
Well, you are wrong, it took me just two weeks to reach steps 5-7.
I also promise you I was a lazy student and I never used to study and used to get just Ds and Es, as for now, I am top on my class, student of the week 3 times this term alone and above all I am a Math genius which i was the worst at.
Fell free to talk to me again and i will give you all the assistance you need.
Good luck with your exams and hope you accomplish your target.
Oh yeah, one more thing, DO NOT STUDY FROM ONE BOOK, ESPECIALLY CHEMISTRY, AND DON'T HESITATE TO ASK UR TEACHERS.
All your inquiries about from Physics, Math and ICT I will be here to help.