The Wedge Group  Producer Motivation – Inside out 

You can motivate a producer through screaming at them, intimidating them and threatening them, but it won't last long. Once they find out that your tirade is short lived, that you can't be in a bad mood forever and that acting like a jerk is only temporary, they will learn how to deal with it by laying low and out of sight.

If you want to motivate a producer, you have to find out what's important to them.  And, there is an inherent
problem with that… you have to care.  You have to slow down and spend some time with them.  You have to get to know them, their family and their priorities and responsibilities.  From there, you can assist in the
motivation by working inside out.

It also helps to have a system, some people would call it goal setting.  But, it's not the basic one page goal setting that most people engage in.  You have to get them thinking, dreaming and most importantly feeling. It's the emotion that gets people going.  It's structure that keeps them going.

A great book to study for a lot of insight on this is Think and Grow Rich, by Napoleon Hill.