Nokia Windows Phone: Question 6

We’re running a challenge where in you can Win a Nokia Windows Phone. The rules of said competition are detailed in the aforelinked post. There will be many more questions over the coming weeks, here is question 6.

Question 6

Introduced with Windows Phone the Metro Design Language provides guidance for developers who wish to build applications that look and behave similar to those provided as part of the core platform. For example, rather than using rounded corners and gradient colours, Windows Phone is predominantly hard rectangular corners with flat bold single-tone colours.

Suggest a rule of thumb or recommendation that application developers can use when designing/developing applications for Windows Phone that will help them adhere to the Metro design language?