Formation of the past continuous
| Positive sentences | Subject + was/were + verb(ing) | They were talking about her when she walked into the room. | 
| Negative sentences | Subject + was/were + not + verb(ing) Subject + wasn't/weren't + verb(ing) | He asked me why I was not having dinner at the hotel. We weren't playing football when the earthquake began. | 
| Questions | Was/were + subject + verb(ing) | Was she going to the theatre when it started raining? | 
Exceptions in spelling
| Final 'e' is dropped (but: 'ee' is not changed) |  | come – coming (but: agree – agreeing) | 
| After a short, stressed vowel, the final consonant is doubled |  | sit – sitting | 
| 'L' as a final consonant after a vowel is doubled (in British English) |  | travel – travelling | 
| Final 'ie' becomes 'y' |  | lie – lying | 
Signal words: 'when', 'while', 'as long as'.