What are some of the most effective actions a manager can take to improve productivity and motivation of his staff?

I agree with what's written in previously , also I may add some points like:

- Empower them, give them the feel of leadership, make them accountable of projects, don't get involved in the details "cu'z you already know it, and people hate this" look for their results.

- Be positive, talk positive, react positive.. even if they did mistakes, let them know how to understand practical lessons.

- Always change or modify their scope, let them know what to expect from you if they succeed, what will be next.

- Finally SHOW THEIR achievements to others if applicable.

Instill a sense of purpose in their job i.e help them understand how their work can make a positive impact and how important it is for the company/project/society. This brings in the intrinsic motivation of human beings and in turn boosts productivity.

I agree with husein, firstly i believe it to understand what are they expecting. By a casual talk with them.

Delegating responsibilities, one on one coaching, bouncing ideas off each other