In an Optional Questions exam, you are given a choice of questions and you have to make a decision about which one(s) to answer. The questions tend to be few in number, which means that each represents a large proportion of the exam. For example, you may be required to write two essays, where each is worth 50% of the exam total.
One of the main challenges here is managing your choice of questions. It's usually possible to entirely avoid any issues by following the Minimum Work Principle, since you will already know in advance exactly which questions you are going to attempt. If you have not done this then it is important that you are able to cope with choice-related problems.
In any case, the very first thing you should do is read all of the questions which are applicable to you. Ignore those which you are certain you will not attempt. Cross them out so that they are out of your mind. Not only is this initial read-through critical in ensuring that you pick the best possible set of questions, but you are far better off discovering any nasty surprises or potential problems at the start rather than halfway through the exam.
Even if you know exactly which questions you will be answering, the initial read-through allows your mind to begin preparing answers in the background. Don't skip this step.
Only when you have read through all of the questions should you decide which of them you will answer. You will save time and maintain a level head by taking a few minutes to make good decisions at the start of the exam. Otherwise, you may find yourself encountering a very common scenario whereby you begin to answer a question and then realise one or more of the following:
This problem is fully preventable and is always the result of not carefully reading and considering the full set of questions before answering. The amount of time you save by rushing into a question is lost many times over if you end up in this situation.
Sometimes, there may be no questions available that you feel comfortable in answering. This is unfortunate but the worst mistake you can make here is to panic and waste time dithering between two or more questions. Read the questions carefully, make a decision and commit to a question, and then stick to that decision no matter what.