It is very difficult to answer all questions during the exam. But the following tips will help you to score better.
Read the question paper for 5 to 10 minutes. The first answer that you write/choose always takes a lot of time than you have anticipated. But don’t worry. This time will be covered eventually. Answer all known questions in the first 1 hour. In the next hour, try to answer all confusing questions. Finally, think about whether you can answer the remaining unknown questions.
If you are left with the last 10-15 mins of time and have to cover more questions, then try to finish the easiest and 100% sure answers in an objective exam. If the negative marking is not allotted, mark all answers without reading questions. If it is a descriptive exam, then writing a few sentences for all questions fetch more marks than completing a single question. It feels the paper is completed.