When do I use View Models, Partials, Templates and handle child bindings with MVC 3

new to mvc3, i have a few questions, would appreciate if someone could answer/provide links:

1. When should I use View Models? Is it not recommended to use the domain? I find that my view models are copies of my domain objects, and don't see the value...
2. When should I use Partials? Is it only if the partial view will be reused?
3. When should I use Display Templates and Editor Templates? Can I use these without a view model?
4. How do I create an edit screen where the parent and list of child objects are both editable? i.e. a few fields at the top (parent) and a grid of fields below (like editable rows), particularly, how do i do the binding? automapper is not used.

Thanks!