I just entered AS level , and took Chemistry . I would suggest u to start making notes from day 1 and revise all the work done at school, let it b 10 mins at least . Secondly , u must b crystal clear about every Chemistry phenomenon, and u must memorise every formula required e.g (moles = mass/mr) . Thirdly , b vigilant as much as possible , do not b lazy and procrastination shud b avoided at all costs . BOL