1. Pick up a technical book on C#. Any book that introduces most of the useful features of the language is fine. Someone else may be able to give exact recommendations.
2. Read a chapter on the book, just far enough to learn about a new feature or two.
3. Code a much-simplified version or a tiny self-contained portion of something you'd eventually like to be able to build. Be sure to A) pick a task that is 5% more difficult than you're currently comfortable with and B) apply at least one technique you just learned about in #2.
4. If you're a master in C# programming, you're done. Otherwise, repeat from 2.
I recommend a book so that you'll be able to find out about techniques you simply wouldn't be able to come up with on your own, to know what's out there and to know what to google for when you need it. A book alone doesn't stick though so it needs to be applied right away. If you can complete steps 2+3 in a day/evening then you'll get a nice mental note of it: "Today I learned xxx."
