Your choice of course is very important. A clear passion for your subject and a keen interest in pursuing this passion well beyond the school curriculum will not only make your time at university happier and more satisfying but it will be specifically tested in the application process and could be decisive.
The University offers a video with some advice about choosing your course here.
Obviously aptitude and achievement to date in your chosen subject area(s) – as evidenced in your school work and certificates (see Qualifications) – are very important to get over the first hurdle but in the Application Process the emphasis is very much on how you will fare with your subject in the future rather than how you have done in the past.
30 undergraduate courses are offered covering 65 subject areas. Further details can be found here. Clicking on the Course you are interested in will take you to a comprehensive explanation of the course content, entry requirements, resources, open days and much more. You will note that some subjects and subject combinations are desirable or even essential before you can consider applying for a particular course.
As well as being able to understand what and why you want to study now, you should also reflect on where you want this to take you beyond your undergraduate life. The course web sites include information on possible career opportunities and employment prospects.