I did AS Spanish last year, and in March we had the chief examiner for AQA come in and do our speaking exams. He also gave us a lesson on how to write essays (hopefully this will help).
He recommended that we started off by doing a 5 minute plan, laying out your advantages/disadvantages in a table, or a sort of mini mind-map of ideas and things to say. This can also help start thinking more deeply about the topic.
He then recommended doing a very short (2-3 sentences approx.) introduction, outlining the issue and saying what you're going to talk about.
For the main part, it varies. If its a question is like 'is alcohol good for society?', it's maybe best to do two paragraphs, each coving both sides of the argument. However if the question was like 'what are the main issues to young people in modern society?' there isn't really two sides to the argument, so he said you could do 3 shorter paragraphs coving the various issues you choose to talk about.
From what I can remember, he said try to use at least 3 different tenses inc. one like the subjunctive to get higher marks. Even just trying to use it - but not executing it perfectly - gets marks (I never really understood it but still tried to use it haha).
Then conclude stating your own opinion or overall view, and maybe a new point not covered (basically don't just repeat what you've already said).
For essays I believe it's definitely best to go for quality over quantity. Being concise and clear about your points and not going on about similar issues can really help the essay flow well.
I remember I had a look on the AQA website for example essays for different grades from previous years. It lets you see what full-mark essays are like and you can use them to improve your own essay writing too.
Sorry if its a bit unclear, tried to recall as much as I could!
As for the Reading and Listening I just tried to learn as much vocabulary as possible and did as many past papers as possible.
Hope this helps.