how to be a good computer engineer

As mentioned above, Computer Engineering involves both hardware and software courses. However, you may also be interested in Computer Science, which focuses mainly on the software side (making applications, games, operating systems).

The classes that will help you the most are math, sciences, and obviously computer or programming courses.

If your school doesn't offer any computer courses, there are also online resources that will help you start learning how to program:
https://www.khanacademy.org
https://code.org

Computer engineering (at least where I studied) focused at the boundary between hardware and software: how electricity flows though computer circuits and chips, what that implies for power usage, and what software would run on the chips and what software would interact with those circuits.

So I would suggest you focus on math (trigonometry of course, and calculus if you can get it) and physics -- specifically electricity and magnetism, circuits, and all of that. If your high school offers computer classes (programming, computer networks), of course take those.

If you are wanting to focus on game design, the math is still useful for understanding some of the advanced programming techniques, and the physics classes should be focused on Newtonian mechanics (when a player jumps, what equation describes the path they fall, and how do we tweak that behavior so that it's fun? -- after all we can't double-jump in real life.)

Hello,

A good place to start learning Computers if your still in High School is any Computer classes offered at your school. As a computer engineer you will want to know a little about a bunch of different Computer programs like (Microsoft Office) or Server operating systems like Windows Server 2012, SQL Server 2014, or SharePoint Server 2013. Learning a lot about any of these technologies can really help you build a well-paying career. Knowing a little about Hardware, Hard Drives, Memory, and Video Cards and what each devices does also helps your career and makes you a well rounded Engineer. Technical Certifications such from Comptia, or Microsoft, help grabs the attention of employers & Technical Recruiters looking to hire good engineers so having Technical Certifications is a great help to your career success. Good Luck :)