If you’ve worked on WP7 apps, you probably came across the MetroGridHelper from Jeff Wilcox. If not, what this little helper does is add a grid of squares that helps you align controls in your app’s pages.
If you’re one of those who ignore the commented sections in newly created pages, you might miss that this feature is now included in the default WP8 project. To use it, all you have to do is uncomment the Image tag at the end of the page
<!--Uncomment to see an alignment grid to help ensure your controls are aligned on common boundaries. The image has a top margin of -32px to account for the System Tray. Set this to 0 (or remove the margin altogether) if the System Tray is hidden. Before shipping remove this XAML and the image itself.--><!--<Image Source="/Assets/AlignmentGrid.png" VerticalAlignment="Top" Height="800" Width="480" Margin="0,-32,0,0" Grid.Row="0" Grid.RowSpan="2" IsHitTestVisible="False" />-->