First, think beyond the level one, end-of-course evaluation most people think of. Management is not interested in whether people liked it. They are interested in knowing the people used it and that the applied skills and knowledge added value and made a difference to the organization.
To improve evaluation you need to improve preparation. Prepare managers to prepare their people to come to the course with the right mindset: a learner versus prisoner, vacationer, or socializer. Have people set personal objectives early in terms of what they want to learn. Ensure that each person develops an action plan while they are in class. Help create short-term (60-day) accountability groups (3-4 people) who will support one another in applying what they learned to their jobs. Enlist the support of managers in ensuring that adequate time is given to participants in the first 60 days after the training to really apply what they've learned on their jobs.