Guided review of the rules of preterit stem-changers. Great to use as a class cooperative review.
Teacher writes the skeleton outline on the board with blanks. Students are given a word/phrase on a piece of paper/index card (for use with magnets) or a Post-It note and are tasked with placing their information where it belongs. Everyone then goes over the information to verify that things are placed correctly.
My classes are typically quite large, so I generally aid in a section with correctly and incorrectly conjugated verbs, as well.