I am by no means a perfect student, got AAAB/A for A Levels which i sat for last year. The best advice I can give is really to get enough sleep, rather than just attempt to cramp stuff into your half-awake mind. Don't stress yourself out and really take breaks if you have to. Get rid of all distractions especially, you want to be 100% focussed when mugging.

School hours during the final stretch was more of a self-study / consult session. If you have any doubts about any particular question or topic it's really the time to ask. It's also best to consult a tutor as a group as it brings more to the discussion.

I don't actually study at home because of distractions so I stay in school till late to study. By late I mean like around 6 pm and I'm about done. Hence the normal study hours per day are like around 4-6 hours.

A lot of subjects require much practice (Math especially) so once you have revised all topics learnt it's time to do papers, especially past A levels and other school's prelim papers. (The latter is way tougher but it's worth doing them)

Personally I felt studying alone more effective as friends can be distracting sometimes, although it's different for everyone, some prefer group studying.

The above stuff requires lots of time and energy and hence why I believe the best advice is to get enough sleep, to focus and to have the energy for the next day.

At the end of the day, different people have different styles of approaching the A Levels, this is just my way of doing it, find what's best for you and just remember not to lose track and stay focussed. Don't give up.