A  complete guide to A-level revision:

https://www.cdarwin.com/attachments/download.asp?file=471&type=pdf

Advice from students who have achieved A*s in their A-levels about how to revise:

https://university.which.co.uk/advice/ucas-application/revision-exams-making-the-grade

When should you start revising for your A-levels:

https://www.whatuni.com/advice/sixth-form-life/when-should-you-start-revising-for-a-level-exams/52956/