How can I prepare for an introductory CS college course?

I am currently in Grade 12 and next year I will be studying Computer Science at a university in South Africa (syllabus is here). However CS has a very high dropout rate here in South Africa, more than any other course, and I'm nervous because of that. My experience with programming is limited to Java in the Net beans environment. I understand the basics of programming (loops, arrays, methods and classes, reading and understanding other languages, etc).

My question is how can I be more prepared? I'm willing to learn new languages or take online courses or anything that can help me next year.