1) Regular verbs are formed in the simple past by adding "-ed" to the base verb. Irregular verbs do not follow a rule and must be memorized.
2) The pronunciation of "-ed" varies depending on the final sound of the base verb, being pronounced as /t/, /d/, or /ɪd/.
3) Affirmative sentences in the simple past use the past form of the verb and a complement. Negative sentences use "did not" and the base verb form. Yes/no and wh- questions use "did" and the base verb form.