Used to

Form:

Used to + main verb

     Example:

He used to walk for a long distance to reach school when he was a teenager.

The negative form:

Usedn’t + main verb               Or                didn’t use to

The interrogative form:

Did + subject + use to + object?

      Example: Did you use to smoke when you were young?

Use:

Habitual actions in the past. (the action isn’t true anymore since there is some interruption with the past)

Warning:

Don’t confuse between the modal used to and the verb to use. Each one has its own independent meaning and use.