As I started out learning about how to get an OAuth2 access token to use the Office 365 APIs, I created these "cheat-sheets" for myself. I realized that they might be helpful for others, so I've cleaned them up and posted them on GitHub. Right now I've got a guide for manually registering your app, and one for parsing your access token to look for problems. Check them out here: https://github.com/jasonjoh/office365-azure-guides.
Feedback is welcome, either in comments here or on Twitter: @JasonJohMSFT.