Hi young man/lady,
A. TACTICS: Yes partly, doing numerous past exam papers will help; first, look at the Qs, then read up, prepare all you can (books, internet, etc. [mrothery.com is very good], then sit yourself down in a simulated exam situation with mum or dad as invigilator, and do the paper without ref to books, etc and mum/dad timing you strictly.
EXAM TECHNIQUE: This is an acquired skill (mainly); (a) answer the question (nothing else)
(b) think: don't just vomit out what comes to your head; work it out
(c) learn to work out from the Q what the examiner is looking for: then put down exactly that: IMAGINE YOU ARE SAYING TO THE EXAMINER: "Thank you for the Q sir/miss, this is what you were looking for; that is what I have put down; Can I have the two marks that are assigned to this part of Q, please? Thank you!"
(d) (tough as it might seem), be positive/confident stemming out of rock-solid preparation: there is overwhelming evidence that optimistic students are the best achievers.
(e) be fresh/alert/active on exam day: DO NOT work till midnight the night B4: that last minute cramming is useless - the examiner can only see what you put down on paper, and if you are feeling tired, dopey, bored in the exam room, you will not put down much sensible stuff. Go to a film the previous afternoon (or listen to relaxing music ("Santana, Ravi Shankar, etc. [ask Dad!!] or "Work Hard, Pay Hard"!!) or cheerful music [e.g. "Happy" by Pharell Williams], and go to bed latest 9.30/10 a.m.
B. STUDYING:
1. Study at a quiet time . e.g. early morning when you are fresh and everyone else is dozing.
2. Switch off distractions like mobiles, internet, so you can concentrate.
3. Take my Dad's advice: "Change of work is rest" - give yourself variety: if you are getting fed up or getting nowhere with something, switch to a different topic/scenario or even different subject.
4. Look after your general health: nutrition, hydration, exercise, recreation, friends.
5. Find a very good tutor who can oversee/guide you and your progress.
May I ask what other subjects you are doing at AS?
Hope this helps!
Mukesh.