If you are looking to build an app for Windows Phone 7 there are steps you have to take before your app is Certified for Windows Phone 7 and added to the Marketplace.
These are the top 7 things to check according to the Windows Phone 7 team including my own tips to successfully get your app Certified for Windows Phone 7.
1. Technical Support Information. Include technical support contact information, such as an email address or URL, within the application along with the application version number.
I would personally recommend if you are going to use an email address, make sure you don’t use an email address you use daily for personal use. To be frank and from personal experience. While you will get legit emails from users who may have a problem chances are there will be an amount of spam as well.
2. Content Validation. Be sure that application visual elements are visible and legible in both Windows Phone 7 light and dark themes. The application description, the UI text, and media within the application must be in the corresponding target language the XAP supports.
In a nutshell, make sure your app is easily viewable. Don’t just toss an app together with a huge amount of buttons and hope that everyone will be able to figure out what is going on and how to use it.
3. Application Termination. Applications must provide a user-friendly error message when an application terminates unexpectedly.
Make sure to add Error Handlers in your code. I myself have been guilty of this and it isn’t just me, major companies do it all the time. This not only helps the user figure out what has happened but if you have Error Handling you will be able to easily narrow down what the problem may be and spend a lot less time trying to track it down (trust me on this one).
4. Application Screenshot. Screenshots must not include any emulator chrome, be graphically enhanced, or use transparent PNG image files.
Basically, take a screenshot of key areas that highlight your app which attracts a user to want it and do not edit it in Photoshop!
5. Windows Phone Marketplace Iconography. Icons must closely match the icon provided in the XAP package.
Make sure your icon matches your app. Too many times you will find an app that you wind up not remembering what it is because the icon is completely different than the idea behind your app.
6. Declaring Application Capabilities. Use the method documented at How to use the Windows Phone Capability Detection Tool. Pay close attention when referencing the WebBrowser control and be sure to access it from code-behind.
To not confuse anyone, it would be in your best interest to visit the provided link and give it a read. It will better help you to understand what this means.
7. Application Localization. Follow globalization and localization best practices on MSDN and test applications using multiple regional and language settings.
If you have the capability of creating a Multi-Language app, do it! Not only will this better help users that may speak a different language it will also open up a larger consumer base to Download\Purchase your app in a variety of countries.