[juped]

This is actually pretty hard. I recommend reading C codebases, but it can be hard to know which ones are good. Code to C99 for now; keep an eye on C11 etc. Have a personal library of C implementations of things. Don't worry about being on Windows, although if you're doing Windows development C#/.NET is the lowest friction path.

I'm writing a book on C. I don't think it will ever be finished or see publication. I recommend writing a book yourself - it's a great way to learn, and maybe you're a better writer than me and will publish it.