Talk to managers. Once someone has gone through training, bring the manager into the picture. Connect learners with mentors. Ask training graduates to be mentors for new learners. This gives learners extra support and reinforces the graduates' own learning.
Track calls to the help desk.
If you've just finished teaching a technical skill, keep track of help desk calls for two weeks after the class. If people are regularly calling the help desk with questions about skills they just learned, something's wrong with the training. That means it's time to take a good, hard look at the training program and figure out how to teach these skills more effectively. Reinforce, reinforce, reinforce. Do everything you can to make sure learning doesn't stop when the class is over.