If you do Windows Store App development you know they want you to get those margins correct! I got tired of looking up the margins guidelines for each app as my mind has problems remembering numbers (I can remember all my clothes and all the thousands of combinations I can create, but cannot remember a pin code or birthdays) and therefore I created a cheat sheet based of the MSDN article on the Grid System / Layout.
Click on the image to see the fullsize version
The colors show the recommended space between items, as well as recommended header space and left margin. Leave a bottom margin as well if there is not scrolling that way (bottom margin not mandatory), and it would make sense to leave a margin to the right as well if you don’t have content that scrolls that way.
Hope this helps, and feel free to give me some tips on some other cheat sheets I could make 🙂