only best wishes will not ensure a better result in the exam. If you had not studied so far, don't lament over it. Try to utilize the time you have got now.
1) Group study: Assign parts of the syllabus among your friends in the group and discuss them.
2) Don't get panicked. Just concentrate on how you can reduce the loss by studying attentively. Frankly speaking, in most cases lessons are memorized faster during exam period than normal time.
3) Have healthy diet: eat lots of vegetables, fruits, milk and of course water (though many of you will now prefer coffee or tea).
4) Try to have a sound sleep before the exam date so that you can answer the questions in cool brain.
Your honest and hard efforts combined with our wishes will help you achieve your desired result!