In such cases, the imperfect tense is used. There are only two sets of endings for regular preterite verbs, one for -ar verbs and one for both -er and -ir verbs. To conjugate a regular verb in the preterite tense, simply remove the infinitive ending -ar , -er , or -ir and add the preterite ending that matches the subject. Check out the table of regular preterite endings below. Keep in mind that one little tilde can change both the tense and subject of a sentence.