i started working on an app and when you right click on a grid, you get about 14 menu items. i thought it was cleaner to start to nest some of the menus as there were clean "grouping" of menu items but it caused a bit of debate.
is there some guideline or best UI practice on context menus?
A submenu requires extra clicks or mouse movement and should be your last resort. And the mouse movement required really is tricky; you have to move the mouse over that narrow strip of one menu item to the right, to get to the submenu.
Also, a submenu hides the item that the user may have been looking for, whereas normally it would have been in plain sight.
14 items isn't that much; for reference, my Firefox context menu contains 14 elements and I can find what I want real quickly. It is much better to group the items sensibly, with some separators in between, and maybe add clarifying icons.
I would say maximum one level of nesting. And nesting only for rarely used actions, its a major hassle to use, especially for inexperienced users (i.e. your grandma).