If you are considering choosing computer science study in Canada, your post-secondary planning process should begin as early as high school. Computer science programs in Canada can be competitive, so it's important to plan your high school courses accordingly. International students in computer science tend to struggle for reasons that have very little to do with computers. More often than not, such struggles are rooted in weaknesses related to languages and math. So load up on math classes. Focus on algebra and if you have an opportunity to take another math, go with geometry. Trigonometry will be useful too, but you will gain a lot of this knowledge in high school math classes even if you don't take a specific class in it. Make sure that you can meet the minimum English or French proficiency requirements by taking any English or French and communications classes in high school. Undertake to read and study independently. This is a good way for international students to develop interests, expand knowledge and improve the vocabulary and reading comprehension skills needed for school in Canada. This will also help you if admission requirements include a personal essay, since you will be able to impress the committee with the knowledge you have built up of terms and issues specific to this area of study. International computer science students often have the greatest difficulty with writing and English classes in their first year of post-secondary study.
There are several additional things that you can do to prepare and increase your chances of being accepted:
Gain experience in the computer science field. Job shadowing, talking with a professional, or attending a summer or spring break computer science camp in your home country are all recommended activities.
Admissions committees may also be interested in international students' personal qualities, which can be developed through participating in extracurricular activities. Consider joining or even starting school clubs, whether related to your area of interest or not. This is also a good way to develop demonstrated leadership skills, which are an important aspect of any competitive application.
Work experience - paid or volunteer - can also increase your chances of being admitted, particularly to programs involving internships, and is an achievement often regarded highly by admissions committees.