There is not particular method to solve these types of questions. It is advisable to skip these types of questions and not waste too much time trying to visualise each of the options.
When you have finished all of the other questions and have some time left, then cut the nets out of the question paper. (You can bring scissors to the exam but please check with the exams officer first!!)
If you have unbelievable visualisation skills and you are sure that you can obtain the correct answer in a reasonable amount of time, then go ahead and answer the question.
When you cut the nets out, you will realise that nets Q and S can form squares but not P and R.