Factory Manager Question:

1) In a meeting with your boss, for example, mention something one of your workers did well. If your boss happens to mention to that worker that you said something good about them, they're likely to feel that you appreciate them and made the effort to put in a good word. That sort of compliment doesn't go unnoticed.
2) Privately laud what your employees do well. Tell them when you have a moment. Go into detail. A private chat, however short, can have a positive impact on morale, resulting in more self-motivation.