Jason Z. of the 37 Signals crew writes when web developing, the first step is to start.
While it would be easy to recommend stacks of books, and dozens of articles with 55 tips for being 115% better than the next guy, the truth is that you don’t need learn anything new in order to begin. The most important thing is simply to start.
I’d go one step further and say this is true for any creative project. Just start. Don’t worry about what you don’t know and focus on what you do know and build from there. There will be moments when you’ll need to learn something, but to think you need to know everything up front will only fuel the analysis paralysis, or bluntly, instigate the fear of failure.