"Quick" questions are brief questions, often compulsory and set in Section A of a paper. They are designed to test whether you have understood the most basic ideas of the course. If you know your stuff, they should not take long, and a brief answer will be adequate.
Standard questions begin with a bookwork question, followed by a problem, sometimes with a more tricky point at the end. Notice the division of marks (usually shown in the margin), and make sure you earn the easy bookwork marks. An annotated diagram or graph may be worth many lines of writing. Always review what the problem will involve before starting the question, and tell the examiner at each point what you are doing. Review your strategy before starting on lengthy algebra. If your algebra falls in a heap and you don't have time to sort it out, tell the examiner what you were trying to do. In numerical problems, get the formula first and then substitute the values and don't forget to quote the units. If you get stuck with a particular part of question, look for "re-entry points" later in the question rather than giving up altogether.
Essay questions are full-length questions designed to see whether you understand some topic in reasonable depth. Stop to think how you will tackle an essay. Your answer must be structured, and you should make an attempt to explain yourself clearly, and to exhibit the logic of the subject and the relations between ideas. For many topics an essay should refer to both theory and experiment. It will normally contain some diagrams and equations, but it must also contain proper headings and connected English, though under exam conditions you will not have time to write a very elaborate account. Writing good essays requires practice - make sure you get some. It is just as possible to get high marks for an essay as for a problem, and you are less likely get completely stuck.
"Brief notes" questions are usually half the length of a standard question, and test your understanding of bookwork. They will not usually need extensive structuring, and your answer might well consist of little more than appropriate diagrams, graphs and succinct bullet points. Before you finish, ask yourself whether you've covered all the important points.
In answering any question, remember that its scope may not be limited to a single course, or to the work of the current academic year. From time to time, Part I material may be very relevant to Part II or Part III questions.
Many questions ask for a formula to be derived. It is of course acceptable to use the desired result to guide your working. However, the Examiners have recently noticed a significant minority of students who get from a wrong starting point to the correct result by "fudging" the working in the middle of a question. This strategy, which borders on dishonesty, is likely to be heavily penalised by the Examiners. If you cannot quite get to the answer, then honesty is the best policy.