"Was" is used for singular subjects (one person or thing):
* The dog was happy to see me.
* The movie was very long.
* She was at the store earlier.
"Were" is used for plural subjects (more than one person or thing):
* The children were playing in the park.
* The books were on the shelf.
* They were excited for the party.
"Were" is also used with the pronouns "you" and "they":
* You were right about the weather.
* They were planning a surprise for her.
Here are some examples of sentences using "was" and "were" in different tenses:
* Past simple: She was tired after the workout.
* Past continuous: They were watching TV when the doorbell rang.
* Past perfect: We were surprised that they were already there.
* Future simple: I was going to go to the concert, but I decided not to.
Note: "Was" and "were" are the past tense forms of the verb "to be."