How do I scroll to the top of a list?
As far as I know, there's nothing built into the OS for that. 

I guess it depends completely on the developers of the app you're using. I've seen some apps where, once you start scrolling, a "handle" appears on the side of the screen that you can tap-and-drag to scroll faster. I've even seen an app or two where you could touch the top of the screen to immediately scroll to the top of whatever multi-screen thing you're looking at. But it's certainly not universal.