More specific advice depends on what your background is and what you're doing now. (For example, are you a student? A CS student? How much of a CS background to you have? Are you working full-time? If so, does your job involve programming? Do you have time to hack on the side?)
Although we have two courses on System's design and System's engineering, teachers here are not very good, and I feel I didn't learn almost anything from them. That's why I want to read more about it and really improve my skills there.
At my daily job I work on several short-time projects, using MS technologies. Sometimes I code .NET, do some basic design for an application, but nothing really big. I don't stop and think about scalability, performance, etc. Those things usually come unannounced later when the application starts to fail in some environments. So, you can see, I'd benefit from learning more about System's design.
Once you've done that, you'll understand a ton about how to think and how design decisions will affect you later on.