This is a great practice for students to catch common mistakes with the irregular preterit/pretérito irregular. Students will read 15 sentences all with 2 different preterite conjugations. They must mark an 'x' over the incorrectly conjugated verb and write the correct form to the right of each sentence.
Since these verbs cause many mistakes, students will then need to recall the 15 verbs' infinitives that they found in each sentence. It makes for a nice reminder to remember the irregular preterite conjugation rules for these verbs.
This is a great activity for homework, whole-class activity, cooperative learning, etc.