What is the best preparation for the Oxford TSA?

Practice! While the TSA differs from ordinary school exams in that there is no content to revise for as such, it is not the case that there is nothing to prepare for! There is a definite skill to answering 50 multiple choice questions in only 90 minutes. Going through past papers and doing problem solving and critical thinking exercises on a regular basis will not only make you sharper when it comes to the real thing but help you to work out an individual strategy or approach to the test. Similarly, writing a 30 minute essay on a random topic is not a typical request and a well honed essay technique and approach to essay plans will make all the difference.