This is an interesting article that provides some good strategies for giving HMK that are reminiscent of things we cover in Educational Psychology..
Spaced Repetition - instead of concentrating study of information in single blocks, have students work with the same material in briefer sessions [even along with other information] spread over a longer period of time.
Retrieval Practice - using tests to reinforce vs. assess what students know.
Making students work a little harder to understand information [so they recall it better] through:
Cognitive Disfluency - e.g., leaving blanks or missing letters; or
Interleaving - mixing things up vs. grouping similar things by type.
[Sean I thought of you as I know you're interested in the role of HMK]