The simple past is expressed using aux verb た(だ).
- 彼は野球の選手だった -> He was a baseball player
- 彼は部屋の掃除をした -> He cleaned his room
- 昨日彼女と話した -> I talked to her yesterday
- あんた今おならした？ -> Did you just fart?
- その本は若い頃読んだ -> I read that book when I was young
The past continuous/progressive aspects are formed as verb+で(て)+いる+た.
- 彼女は寝ていた -> She was sleeping
- 当時私は沖縄に住んでいた -> At that time I was living in Okinawa
- ご飯を食べていたら地震があった -> I was having a meal and there was an earthquake
Just like in the present tense, the imperfect past aspect is often expressed using the continuous/progressive aspects:
- 私は以前車を二台持っていた -> I had two cars before
- 上手く行かないことは分かっていた -> I knew it wouldn’t work
Note continuous/progressive actions in sub-clause are often in the present tense even for the past:
- ひげを剃って.いる/いた.時に電話が鳴った -> My phone rang when I was shaving
- 私はご飯を食べて.いる/いた.ところだった -> I was in the middle of having a meal
“Used to” or “would” is often expressed as よくした (did often).
- 私は昔はテニスをよくした -> I used to play tennis often
- 子供の頃親父によく怒られた -> Dad used to scold me all the time when I was a kid
よく can be substituted with similar words like しょっちゅう, 何時も, etc.
The past continuous is often used to express “used to” and/or “would” as well.
- 彼女は昔銀行で働いていた -> She used to work for a bank
- 私は昔オートバイに乗っていた -> I used to ride a motorcycle
- 私は昔海辺に別荘を持っていた -> I used to have a summer house on the beach
ものだ/ものだった is often used to remember about the past, usually reminiscing. ものだ often becomes もんだ in conversations:
- 子供の頃この川で泳いだものだ (もんだ) -> I would swim in this river when I was a kid
- 大学生の頃は皆で夜通し話をしたものだった (もんだった) -> We used to talk all night long when we were in college