How to get the ViewModel to communicate to the View's code behind file.

I am wondering if someone can point me to best practices of communicating from the ViewModel to the view's code behind. I would guess events/messaging etc but would like some input on it. There are UI changes I would prefer to keep out of the XAML file (for some reason I find XAML files with lots of markup for logic ummm, 'smelly'?). But I'm trying to be a good MVVM boy so I don't want it in ViewModel. Any pointers or examples out there you know about would be appreciated.