What requirements do I need as a Student in highschool to prepare myself to get a higher rate of acceptance in Universities in different countries

Med School Questions High School
1

I live in Qatar, currently doing my IALs and I plan on Studying in Qatar, Canada, UK, Australia. My AS results are 2A, B & C. What should I do right now in highschool where it would help me in getting in to universities easily in the different countries listed.