Use the past simple to talk about activities or routines which take place at a specified time in the past. Notice that all subjects take the same conjugation of the verb. Regular verbs end in '-ed'.
visit - visited
enjoy - enjoyed
Irregular verbs have various forms and each verb needs to be learned.
see - saw
think - thought
The past simple is used to express a finished past action which occurs at a specific moment in the past.
Examples
She visited Iran last month.
They didn't go to Tom's party last weekend.
Where did you go on vacation last summer?
The following time signifiers often indicate a specific point in time.
last
ago
in ... (plus a year or month)
yesterday
when ... (plus a phrase)
Examples
They had lunch at home last week.
He left the company many years ago.
Susan bought a new car in May.
He telephoned his friend in Rome yesterday.
I played golf when I was a teenager.
Positive Form
Subject + past form of verb + object(s) + time
Examples
They flew to Chicago last month.
Peter completed his course three weeks ago.
Negative Form
Subject + did + not + base form of verb + object(s) + (time)
Examples
They didn't expect to see you at Christmas.
She didn't understand the question.
Question Form
(Wh?) + did + subject + base form of verb + (object(s))+ (time)?
Examples
Where did you study French?
When did you arrive last week?
http://esl.about.com/od/beginningenglish/ig/Basic-English/Past-Simple.htm
