1. Sign up for ArcGIS for Developers (it's free!)
- Access to tools on ArcGIS Online and the ArcGIS for Developers website.
- 50 service credits every month to develop with services such as routing and geocoding.
- Community support on our forum.
2. Setup a local development environment
The Mozilla Developer Network has an excellent guide on setting up a local development server.
3. Hello World
4. Keep learning