*i just wanted to clear up the difference in years since it's different depending on your country or school: when i say year 12, that was junior year for me and year 13 was senior year*
WHAT I DID
do as much as you can in year 12
seniors are very serious when they tell you to finish as much as you can in year 11. the ib has a huge workload, and putting off until year 13 won't make that go away. i had first drafts written for my extended essay, tok essay, two internal assessments, and the final draft of one written assignment before year 13 started, and i'm so glad that i did. it saved a lot of stress and i could send my drafts to my teachers as soon as school started.
start the extended essay early with a topic you love
i was really glad i started thinking about the extended essay early, because, like everyone else, i wasn't sure what topic i wanted to be writing about for 15 months. as soon as we were introduced to the extended essay, i started writing down possible subjects then possible topics for myself. i ended up writing about the differences between percy jackson and the sea of monsters and the odyssey. percy jackson was one of my favorite book series, and i was very interested in how stories are changed to make them suitable for children. i ended up loving this topic and having a lot of fun with it.
don't use coffee as a replacement for sleep
caffeine is a short-term solution and is not a replacement for sleep. caffeine is mildly addictive, so regularly drinking coffee will make it hard to stop, and hard to get a better night's sleep. coffee is obviously ok in small doses, but regularly substituting a regular amount of sleep for a cup of coffee won't do your health or your grades any favors. start studying early and continuously, and you won't have a problem with sleep. i went through my two years of ib without getting less than 7 hours of sleep!
WHAT I WISH I DID
make study guides right away
whatever your learning style is, start making study material for yourself from day one. if you're a visual learner, make study guides with lots of diagrams and charts. if you're a kinesthetic learner, make flashcards with terms and concepts. if you're an auditory learner, record yourself reading the textbook to play back later. that way you have a summary of the topic when you need it. i spent a lot of time in year 12 making study guides. they were useful and helped me study, but it would have been more efficient to make them as i go along topic by topic, not all at once.
start right away on topics you don't understand
if you have a subject with a teacher that you can't really understand or a topic you're having a hard time with, start researching right away. whatever you don't understand will start to accumulate and it will end up as a big mess of trying to understand everything right before the exams. find your resources and just start.
do all your homework from the start
speaking of starting right away, make sure you keep up with all of your homework. if you don't understand something, write it down and ask your teacher the next class. if you still don't get it, look it up. all of the concepts you learn will pile up and you need to understand one to understand the next. don't let it snowball, start your homework right off the bat.
start practicing exam style questions
as soon as you know the first topic for each subject, start doing past paper exams and exam style questions. you'll get used to ib questions and your writing style early. there's a very different approach to writing ib exam questions than to the igcse, for example, so it will take time to relearn.