If you are looking to implement the rating control in your windows phone 8 app which lets the users to rate an item within the specified values/stars , here’s an useful control from Windows Phone toolkit called “RatingControl” which can used .
<Toolkit:Rating Height="30" Grid.Row="1" Value="0.6" ItemCount="0" x:Name="ctAbundantcodeRating">
You can download Windows Phone Toolkit via NuGet manager from Visual Studio 2012.