Make sure you know what resources are available. Find out about seminars and study guides, ask your professors for applicable courses in college. Also, talk to other students who have taken some exams. Having come from a different education system, you may be used to different studying techniques. Doing this research will help you figure out if you need to modify your study habits.
Many international candidates find the preliminary mathematical exams easy to adapt to.
The essay exams, can be a different matter. The exams are only offered in English and French, and for someone without sufficient background in these languages, it can be an obstacle. It's never too early to start improving these critical communication skills. Try and take a lot of writing and speech classes while in college to improve your communication skills. Improvements in conversational skills will also help you get the job you want.