How to get A/A* In Biology and Chemistry?

Hi Im in Yr13 and Id like to know how do people get As and A*s in Biology and Chemistry.
In Biology i find the mark schemes to be way too specific and sometimes hard to figure out what the question is asking.
Chemistry it is different you just have to know all about Chemistry but if you do the mark schemes arent as picky and more flexible to me.

So how? Biology is so weird with its mark scheme.......

Are you asking the same question as me? I think I've posted this question twice. No one has quoted me so I assume no one has responded and I don't know how to find my thread. About the mark schemes, they're not really that hard to understand, in chemistry it does say more of "you need to know this exactly and this" whereas biology might be a little more generic.

As for how to get an A*, I read this....
http://webcache.googleusercontent.com/search?q=cache08tvCCJGbgJ:www.ocr.org.uk/Images/16356-a-level-a-frequently-asked-questions.pdf+&cd=1&hl=en&ct=clnk&gl=uk

I'm not really sure what to do here. This pdf was published in 2010 as far as I'm aware. It suggests that for an A* you basically need at least 80% UMS in AS modules and at least 90% UMS in A2 modules.

I even sent an email to OCR but they haven't responded yet, then again it's only been a day. I've asked my biology teacher and there doesn't seem to be a general consensus. It's always been 90% in the past though. The problem is that I must know if I need to resit my AS exams so I must know this information. I have a deadline for handing in resits in November. Damn it all.

I don't care. I'm going for over 90% in everything if they don't respond.

But the thing is to get 90% you can never be too sure of what you got right. You cant feel the same confidence as you would do from doing a maths exam. know what i mean?

But the thing is to get 90% you can never be too sure of what you got right. You cant feel the same confidence as you would do from doing a maths exam. know what i mean?