Things you should (and must) know before you design and develop cross-platform applications! And even if you are developing your app only for one platform, it is always essential to know the official design principles for the platform you are developing for.
Cross-platform guidelines for developers:
Follow these Cross-platform guidelines from Google, Apple, and Microsoft before you develop your application, note that there are also guidelines for the wearable devices (smart-watches etc.). Check out the attached URL’s below, and you are welcome to share more useful information!
- Android (Mobile): https://developer.android.com/design/handhelds/index.html
- Android (Wearable): https://developer.android.com/design/wear/creative-vision.html
- Material Design Guidelines: http://www.google.com/design/
- Windows 10 Universal: https://dev.windows.com/en-us/design
- Microsoft’s UX Principles: https://dev.windows.com/en-us/desktop/design