Past Tenses

 Past Simple
Normal narrative past form (sequentially occurring actions).  Example:

When I came home last Monday, I had a message on my answering machine.

It said, “Meet me in the park.”

I didn’t know who the message was from, but I was curious.

I put on my jacket, took my bag and went to the park.

And there he was: Luke, an old friend from school.

I was glad to see him and he looked relieved. 

Past Continuous
It emphasises the progression/process of an action. Describes actions which were happening in the past. Example:

The sun was shining.

He was standing there smiling at me.

In his hand he was holding a flower.

Past simple and continuous can be used together to indicate that one action interrupted the other one. While usually is used with past continuous and when with past simple

We had a coffee while we were waiting for the train.

I was watching TV when my mum got home.

When two actions are happening at the same time, we use past continuous for both verbs:

I was reading while it was raining

When one action happened after another action, we use past simple for both verbs:

I woke up and had a shower

Past Perfect Simple
It describes an action that took place before another (previously-mentioned) action. Example:

After I had checked all the messages on my answering machine, I put on my jacket…

I hadn’t seen him for ages.

He was holding a flower that he had bought in a nearby flower shop.

After and before are used to relate facts from a chronogical point of view, pointing out which action precedes or follows the other one.

He celebrated after he had finished his exams

I'd already eaten before we went to the restaurant