Updates to a pst and saving

Very new to this awesome email component (company is now putting in the purchase order, lol) and still trying to learn my way around it.  

(1) When you make changes to an opened pst, like adding a folder or email, is there something you need to call to force the changes to be saved to the pst?

(2) Also what is the graceful way to close a pst down?

Thanks again.