What are best practices for view/orientation reset?

Hi all,
I'm having trouble finding any info on best practices for view resetting in Rift games.

In particular:
1. Should we rely on the system calibration for the view orientation - or is it best to also include some way for users to tap a key to reset their view while playing?

2. Assuming we do offer some key combo/UI option to reset, should we reset the position only, or the position *and* the orientation?

3. is there some best practice for things such as a countdown mechanism, or should the reset happen the moment they press the key?

Thanks!