Steps to building your app
Download the Getting Started Guide.
Find a helpful overview on the Windows Dev Center including learning tools, code samples, templates and more.
Try a Hands-on Lab with exercises to get you started.
Windows 8 app developer blog - Insights on building Metro style apps for Windows 8, by the Windows 8 engineering team.
Info on Debugging and Testing Windows 8 Apps.
eBook on building Windows 8 Apps.