Well Begun is Half done. That is pretty much true.
- I search about the idea I have. If there are any blog posts/write ups where I can bootstrap from.
- I search GitHub for any implementations available / code samples
I'll do it Phase
- Imagine how I'd want the final result
- Iterate on implementations. Which Language and which framework.
- Ease of Writing.
- Start to Write code till it gets in shape
- Write more code to prettify it
- Show off for my current progress
- Get FeedBack
- Write comments(Very very important) in code/annotate code
- Repeat 2 for any new features
- Blog on it.
TL;DR: There isn't a golden rule to kick something off. I picture how it'll be finally and work on that.