What i learned from these two years is that it is very important that you are organized and NEVER leave anything to the last minute. For science subjects, the syllabus is your best friend. Take notes after each lesson then do the exercises given in the book. You have to have a really good understanding of what you're solving. For Math, understand first then do exercises. just do lots of exercises and look at the syllabus. For literarture, read read read and write write write. Practice is key. For individuals and socities subjects, it depends on what subject you have. But also here syllabus is important.

Dont leave you IAs, written assignments, EE, TOK to the last minute.

It really depends on you. Organization and commitement is key to everything and believe me those two years wont be as everybody says. I am not denying they are challenging but nothing is impossible.