In a high school without any computer science classes, it is hard to be prepared for a computer science major in college. In order to combat this problem, I took as many classes to do with problem solving, mathematics and computer design as I could.
My engineering class helped me improve upon my problem solving skills because the class was centered on brainstorming and designing ideas to help solve problems.
I also took the required math classes so I could take AP calculus my senior year. Calculus helped improve my mathematics abilities tremendously by not only learning brand new concepts but also building upon already known concepts by using them in new and more complicated ways.
Finally in order to improve my knowledge of computer design and code, I took web design. Web design helped me strengthen my code learning skill by learning HTML and applying it to building web sites.