1. Do not leave things till the last minute ( I do... but I try not to)
2. In the remaining 40 days, set your goals: small ones for every day, don't expect to digest an entire topic (unless you are certain you have the ability) - so a timetable might work for you (mine's in my head)
3. If you have questions, don't ignore them, ask teacher, ring up advice line or post here.
4. Ensure that you spent enough time on your weaknesses so you can patch them up (oh dear... English)
5. Form study groups (they might work... well, they work for some people)
6. LISTEN IN CLASS!!! (especially if you are yet to finish all your topics at school) Sometimes the things get into your head faster if you be attentive in class, than going home and read over it 10 times.
7. Lastly, don't stress, please don't stress, when you are starting to get stresses, everything would start falling apart for you... take things easy, and go according to your plan... go take walkies, talk with friends, do some exercises... just try to be relaxed.
GOOD LUCK!! HOPE YOU ACHIEVE YOUR GOALS!!!