Starting y12 with a focus on going to Cambridge

Hi,
I'm starting Y12 in September and because I'm wanting to study something to do with English, not sure yet, at Cambridge, I want to start with the ball rolling. I've done as much prep as I can with the info I've had from my teachers but I was wondering if anyone had any tips/advice for starting sixth form, especially when it's quite a common low class school and I'm wanting to attend such a high standard university. I'm studying English Lit, English Language and History at A Level and I might do the extended project in politics or philosophy but I'm not sure yet. It's results day on Thursday for my GCSEs and I'm quite nervous because they base our predicted A Level grades on them - I'm predicted mostly As/A*s for GCSE so I'll be disappointed if I don't get what I worked for.

Any advice for starting y12?