was/wasn't:

1. He was in the library.

2. I was ill las week.

3. He was asleep.

4. I simply wasn't there.

5. He wasn't that thrilled.

we're/weren't:

1. I were at the concert last night

2. Jessica and John were married.

3. They were friends

4. These kids weren't like me.

5. We weren't the only ones onto this.