The past clauses

1-The past time 
It is used to talk about activities or situations that began
and  ended at a particular time in the past ( e.g., yesterday, 
last night, two days ago, in 1990,…).

Most simple past verbs are formed by adding -ED to a verb. 
And most have irregular past forms.

2- The past progressive 
It expresses an activity that was in progress ( was occuring, 
was happening) at a point of time in the past (at x o’clock) 
or at the time of  another action (when x happened) 
during some time.
When the phone rang, I was sleeping .
= I was sleeping when the phone rang.
= The phone rang while I was sleeping.
= while  I was sleeping , the phone rang.

When two actions are in progress at the same time, 
the past progressive can be used in both parts of the 
sentence.

While I was reading, he was waching TV.

When = at that time (Use the simple past)
While = during that time ( Use the past progressive)

3- Time clause in past time:
When I went to New York City, I visited my sister
Time clause	Main clause
= I visited my sister  when I went to New York city.
Main clause	Time clause

Punctuation : When the time clause comes first, It 
followed by a comma.

When, after, before, while introduce time clauses.
When, after, before + subject  and verb = a time clause

In the when clause (sentence introduced by When), if the action 
happened first, both verbs can be simple past :
When he arrived, he stayed.
( first)                (second)
A clause is structure that has a subject and verb.

4- Expressing past habit:  Used to :
Meaning : expresses a past situation or habit that no 
longer exists at present.

Form : Used to + the simple form of a verb
Example: I used to live in Paris. Right now, I don’t.
egative : Didn’t use to = Never used to
Questions : Did subject use to + the simple form of a verb ?

For some verbs, the simple past and the passive form 
are the same meaning:
graduated = was, were graduated
worried = was,were worried
Stayed = was, were staying
Started = was, were starting
Begin = was, were beginning

 
The passive form ( was, were  + past participle)

Nonprogressive verbs:
Some verbs are not used in progressive tenses:
Hear  - see - believe - think - understand - know - be - exist - 
own - have - possess - belong - long - need - want - prefer - 
like - love - hate - forget -  remember

Sometimes think and have are used in progressive tenses.
When think means believe, it is nonprogressive.
When think expresses thoughts it can be progressive.

When have expresses possession, it is nonprogressive.
Be having good time (In certain idiomatic expressions) have 
can be used in the present progressive.