Read the instructions carefully. Read them again.
If there are choices in the exam mark which ones you intend to do. Do not panic if you can not find enough choices. Exams always look dreadful at first. Read the exam a third time, marking questions you could attempt to answer.
Decide on the order in which you will answer the questions. Start with the compulsory ones first, if there are any. If not, start with your "best" question as this will build your confidence. Then try to tackle one of the hardest questions. It may not be a good idea to leave the hardest ones until the end. If you are short of time, or tired, you will find it even more difficult to answer them satisfactorily.