Used to and Would

used to / would + infinitive

Example: I used to / would smoke.

did not + use to + infinitive

Example: I did't use to smoke.

did ... use to + infinitive?

Example: did you use to smoke?

We use used to + infinitive or would + infinitive to describe repeated actions in the past:
I used to keep the windows closed when I first moved in. (but I stopped doing this)
I would leave the windows open whenever I was at home.
Note: we do not usually use would in the negative form and in Yes/No questions.

• We use used to + infinitive to describe past states that are usually no longer true:
  We used to live in London when I was a kid. (but we don’t now: not We would live in London when I was a kid.)

• We do not use used to to refer to specific restricted periods in the past or saying how long it took or how many times:
  I lived in New York City for ten years. (not I used to live in New York City for ten years.)
  I went to London twice when I was young. (not I used to go to London twice when I was young.)
  Note: we do not use would with state verbs.