One of the biggest excuses I hear from students for poor exam performance is that they ran out of time. Poor timing is a symptom of poor exam organisation. There is no excuse for it.
Exams are designed to create a lot of time pressure. This makes time a very precious resource. Without a clear plan of how to allocate your time during an exam, you will not use it very productively. In the same way, most people without a budget will mismanage their personal finances. The best exam strategy will centre around making the most of the limited time you have available.
The more a question contributes to your score, the higher the priority it should receive. By default, the amount of time you allocate to a question should be proportional to how many marks the question is worth. So you should expect to spend around twice as long on a 10-mark question versus a 5-mark question.
For each exam, create a timeline for your timing strategy. Doing this will help you visualise exactly how you will spend your time and prevent major timing errors. It's very important that you practice your strategy when you work through past papers. Once the real exam starts, stick to your strategy no matter what.
Even if you create a timeline, there will probably be situations where your timing has slipped and you won't have time to finish everything. All else being equal, you should prioritise the questions that are most incomplete. These are the questions with the greatest number of remaining marks to score.
Don’t spend ages trying to squeeze a couple of marks out of an almost-complete answer when you can get a lot more from a question you have barely touched. Just like with your preparation, your attention should always be on whatever will bring the biggest increase to your exam score.
Checking your answers should not be an afterthought. It should be deliberately factored into your plan just like any other aspect of exam strategy. You should allow 5-8 minutes checking time per hour of exam time.
There may be certain questions or parts of questions where you feel less confident about your answers. Keep a record of these areas on some rough paper and prioritise them during the checking phase.
If your answers contain any calculations, these should also be prioritised for checking. It is far easier to make and far harder to spot an error in numbers than an error in language, and they have a nasty habit of carrying through to the rest of your answer.