To form the imperfect tense, you take the 'nous' form of the verb in the present tense. Next, you take the -ons off the ending of the verb so that you are left with the stem. Then, you add the following endings: je - ais tu - ais il/elle/on - ait nous - ions vous - iez ils/elles - aient For example, if you had to form the 'je' form of 'regarder' in the imperfect tense, you work out the 'nous' form of the verb in the present tense, which is 'regardons'. Then take off the -ons, to make 'regard'. Next, you would add the imperfect ending for 'je' which is 'ais', to create 'regardais'. And that is how you form the imperfect tense. (I would then run through some examples to help the student practice, and to see if there are still any other issues)