Keep learning as much vocab. as possible!
When doing the listening, use the time that you're given at the beginning to look through the paper properly - note down translations (in Spanish) of key words that are written in the answers (usually the MCQs) to help you listen out for them in case they come up. Also, take note when questions are using more than one tense (ie. past, present, future) as it's easy to hear a key word and not realise that it's not referring to the same tense as the question!
Be aware of any particular complex phrases that could boost your mark in the writing exam - just things like using comparatives, exclamatives such as lo pasé bomba!, fue inolvidable! or even one sentence in the imperfect subj. (if you've learnt it).
This is from doing AQA, but I'm sure it can be applied to other exam boards too