This only applies to Ti 3.0 and above. For modifying anything below this, it is a crapshot, you will need to look at other manifest files for the format, as each type/view uses a different format.
If you are looking at modifying the manifest by:
Adding or removing an available element - If you do it in visual studio it will help you out. There is something called intellisense in Visual Studio.
Here is a screenshot of that in action.
It will also tell you when you don't have something that you should or that what you have is incorrect if you simply look at the element warning. Here is an example of that warning. You can see the warning by hovering over the blue squiggly underline.
In this case it is telling me that I am missing an inner element by the name of Button. Pretty simple.