how to encourage and not be a nag?

Options
For me this is a tough one. I am never to sure how to approach this.
Asking can be bugging, Bugging is nagging, Nagging is #itching and so on.
There are only so many encouraging words before I think I sound like a broken record.
And how do you respond to giving a positive comment and getting a negative response?
Ladies and Gents. I need some help here.