I'll keep it brief: I'm in Year 11 and am aiming for all 9s. Ask me for help with any of the core subjects - if it's my exam board I might be a ble to help.
Dr Frost is good for maths (IMC, SMC and GCSE preparation).
Litcharts and genius are good for English.
PMT is good for science (and English). Savemyexams is also good for science.
GCSE Maths Tutor for maths on youtube; Mr Salles and Stacey Reay for English; freesciencelessons and cognito for science.
Get a brief overview of a topic before you learn it (ask teachers for a their yearly lesson plan).
Make non-linear notes in class (mind maps).
Revise using mind maps, flashcards, blurting and the feynman technique.
Youtube videos are also good, summarisation is ok.
The pomodoro technique is overrated, just study until you've done enough; timetables are semi-useful (creating a checklist can be just as efficient).
Good luck everyone!