Work hard and work smart. Quality over quantity. Many students tend to associate the number of past papers worked to laureate success. By so doing, they cannot find time to correct their mistakes or revise properly. You do not need to do all papers.
Correction of mistakes copybook. Often as students, we tend to neglect the basic mistakes we make. Be it during classwork, homework, tuition work or past papers. I suggest keeping a copybook from the start of Lower 6 in which you write all the stuff that was unclear or miscellaneous. Add this to your revision checklist.
Be obedient to Cambridge syllabus. Often, our teachers tend to give their own definitions or methods to solve a question. Agreed, it does help in understanding but Cambridge only knows what is in the syllabus and the prescribed textbooks. I would suggest to use your teacher's notes for better understanding but stick to Cambridge's method for the exam. Focus on Cambridge's exam reports as well to be updated on the way students are being assessed.
Teamwork. The competition is undeniable but it helps a lot to have someone or a group with whom you can clear all doubts. Not all teachers would be able to answer your call at 3 am to discuss a question. Having friends who share the same goal as yours is truly a blessing. You gain twice the knowledge. So do preach teamwork.
General paper. This might not apply for everyone but still. If you do not treat GP as a main, it can be costly. Often we neglect the Paper 2 i.e data and comprehension. In my opinion, it is the most decisive paper. Work as much P2s as you can, be it from other variants.
Practice as much as you can. Stick to Cambridge's methods when answering.
The best reference for this subject is the Cambridge textbook. Make mindmaps for all chapters.
Work the old classified textbook, the one which included the 1980s, 1990s questions.
Treat it as a main. Work as much P2s as you can and start working 1 essay per day during exam season.