Most verbs in English form their various tenses consistently: add -ed to the base of a verb to create the simple past and past participle: he walked; he has walked There are, however, a number of so-called irregular verbs, (including, unfortunately, some very common verbs such as to be and to have) whose various forms must be memorized An alphabetized list of Common Irregular Verbs is available in the Guide that you can copy or print out and then try to memorize or at least use in practice sentences You should take the quizzes on irregular verbs, below, after you've looked at this list University of Pittsburgh has a page devoted to the forms (and history) of irregular verbs The irregular verbs listed there are nicely categorized according to form and spelling patterns -->