1) Search contract
The search contract lets your users search through your app’s content from anywhere in the system.
Using the Search charm helps you:
To have a great search experience, follow the guidelines for search.
If the applications implements search contract:
Repeat the steps below:
How to make the test:
Specific to snapped view look for issues with layout changes (results page)
Reference
http://msdn.microsoft.com/en-us/library/windows/apps/hh465233
2) Share target contract
Users will always have information they want to share.
If your app implements the share target contract, it will always be one swipe away for the user.
If you want to increase the usage for your app, and have scenarios that can consume data from other apps, implement the share target contract. Windows does most of the heavy lifting with sharing the data, you simply have to receive it and let the user access it within your app. For more details, check the guidelines for sharing.
Check Manifest for declaration <ShareTarget>
Execute a share operation using the app as the target application and then ensure that:
http://msdn.microsoft.com/en-us/library/windows/apps/hh465251
3) Share source contract
An easy way to extend your application and connect it to any other application or service is to implement the share contract. Participating in the Share contract means that you don't have to write extra code or provide other developers with an SDK for your app just to share content. You will be adding value and exposing it in the consistent, safe way that all Windows 8 users will expect.
For details on sharing, check the guidelines for sharing.
Install SDK sample target and check the below items:
Only share through the share charm.
4) Leverages file pickers
A Metro style app can call a file picker window to let the user browse their system and pick files or folders for the app to operate on or to let the user save a file using a new name, file type, or location ("save as"). Apps can also use file pickers as an interface that enables them to provide other apps with files, a save location, or even file updates.
Leverage file pickers within your app if you want to interact with user data that is stored in files.
To learn more about file pickers and follow the guidelines for file pickers.
Ask if they use file picker and have demo. Appropriates uses cases are:
Check for inappropriate use:
http://msdn.microsoft.com/en-us/library/windows/apps/hh465182