1. When to use Part Simple?
We use the past simple to talk about consecutive actions or situations in the past, i.e. for the main events in a story.
For example: We arrived at the airport and checked in.
2. When to use Past Continuous?
We use the past continuous (was/ were+ verb + -ing) to describe a longer continuous past action or situation which was in progress when another action happened, or to describe an action or situation that was not complete at a past time.
For example: We were having dinner when the plane hit some turbulence.
At nine o'clock most people on the plane were reading or were trying to sleep.
3. When to use Past Perfect?
We use the past perfect (had+ past participle) to talk about the 'earlier past', i.e. things which happened before the main event(s).
For example: When we arrived at the airport, we suddenly realized that we had left one of the suitcases in the taxi.
4. When to use Past Perfect Continuous?
We use the past perfect continuous (had been+ verb + -ing) with action verbs to talk about longer continuous actions or situations that started before the main events happened and have continued up to that point. Non-action verbs (e.g. be, have, know, like, etc.) are not normally used in the
past continuous or past perfect continuous.
For example: We'd been flying for about two hours when suddenly the captain told us to fasten our seat belts because we were flying into some very bad weather.
Source: English File, Upper-Intermediate
by Chritina Latham-Koenig and Clive Oxenden