My daughter got the CGP books along with the ones aimed at getting 8/9s. Look carefully at the spec. Get hold of every past paper you can find - the science has not changed that much even if the spec has been updated.
For each topic make your notes/mind maps/quiz lets/whatever works for you - use the spec to make sure you cover everything even if it hasn't been covered in class. Find every question relating to that topic and have a go at answering them all. Use the mark scheme if there is one when marking and learn from it.
Keep doing questions - some come up again and again with subtle changes in wording.
Daughter ended up getting 8 9s including all the sciences, plus 8,7 and 6 (art).