Figured I'd chime in with stuff I learnt from sitting my exams in 2015 & 2016:
Revs:- Time management (like in all exams) is important. You're probably going to spend the whole exam writing, so making sure you spend an equal amount of time on everything is key, so you don't end up getting flustered.
- Pick the questions you want to do first in reading time, and try to stick to one revolution at a time. For me, I picked the question I knew was going to be most difficult and would require a bit more time, then I did the other part of the exam for that revolution, then I went on to the other revolution, and finished it off with my essay, because I knew I could write it quickly and writing it didn't require much thought compared to the other parts of the exam.
- Make sure you only answer within the time that's specified in the question - so, if you're given a timeframe of 1958-1963, don't give evidence from stuff from 1967, etc.
French:- Make sure you highlight which language you have to respond in! It's such a basic mistake to make, and a lot of people make it each year!
- Use highlighters in the reading comprehension to get the key parts.
- Don't use your dictionary during the listening section - if you don't understand a word, jot it down phonetically, and then figure it out when you have time to write down your answers.
- Likewise, don't worry about writing out perfect answers during the listening - make dot points or whatever, then write things down properly when you have time/at the end of the listening.
- Remember to follow the conventions of the text types in the writing section - whether that be dates, titles, addresses, tone, etc.
- Read your writing piece backwards when you've finished to pick up errors! Picked up this tip from my teacher and it was super useful.
Bio:- Main one is make sure you're answering the question - highlight exactly what it's asking, and make sure you come back to it in your answer if you go off on a bit of a tangent.
- Read the question carefully - try to avoid making silly mistakes!
For the others, I don't think I have particularly specific advice.
Just manage your time well, make sure you know what the question is asking you, and you'll be sweet. Try to answer every question, too, even if you're stuck and don't really have much of an idea.