I'm targetted to get an A in biology AS and have consistently done well in our weekly tests, so, it looks like it'll happen. But, I don't find the subject easy, i revise to do well, so, I'm talking as someone whos in a similar position to you, but has got a method to suit her. For me, the key to doing well is thoroughly undertsanding the stuff. If you know why something is the way it is, you learn it, and remember it, because it makes sense. That means when asked a question, irrelevant of how its phrased, its easier to answer, because you no the words their using and the context. So yeh, make lots of notes, and make sure you undersatnd it all.
We haven't started yet, 'cause it's pointless to do so now, but when you get closer to the exam date, do past papers, as everyones said. But do that in the mind to get used to the exam, how they ask questions, interpreting how much a question is worth in terms of how much to write etc (generally familiarisation) not to memorise what's asked and word for word what to write.