We use the past continuous tense when we want to talk about an action that was happening (or was in progress) over a period of time in the past.
     
     We form the past continuous or past progressive like this: 

     –  Affirmative: subject + was/were + verb –ing + complement.
     –  Negative: subject + wasn’t/weren’t + verb -ing + complement.
     –  Questions: Was/Were + verb -ing + complement?

Examples: 
     –  I was arriving home when you called me.
     –  We were watching a movie when the lights went out.
     –  Mary wasn’t sleeping when the concert started.
     –  Were you talking to Lucy when I called you?

     Remember to follow these rules for the continuous tense:

     1. If the base verb ends in a consonant preceded by a vowel, the final consonant is doubled.

      Examples: swim + ing = swimming / run + ing = running

     2.  If the base verb ends in “e”, the final “e” is deleted and then we add “-ing”.

      Examples: have + ing = having / shave + ing = shaving / take + ing = taking

     3.  If the base verb ends in “ie”, we change “ie” for “y” and the we add “-ing”

     Examples: die + ing = dying / lie + ing = lying

Practice this lesson here: PASC001.