USED TO

WE USE USED TO TALK ABOUT:

A PAST HABIT THAT IS NO LONGER TRUE:

I USED TO BITE MY FINGERNAILS (BUT I DON`T BITE THEM NOW).

A PAST STATE THAT HAS CHANGED:

HE USED TO BE INDECISIVE.(BUT NOW HE IS MORE DECISIVE).

TO TALK ABOUT A SINGLE ACTION, YOU MUST USE THE PAST SIMPLE:

I USED TO GO TO LONDON IN 2001.(WRONG)

I WENT TO LONDON IN 2001.(RIGHT)

WE FORM THIS STRUCTURE WITH SUBJECT + USED TO + INFINITIVE (WITHOUT TO)

  I / YOU/ HE /SHE/   IT/ WE/ THEY
Affirmative JOHN USED TO WORK IN THE MOVIE INDUSTRY
Negative THEY DIDN`T USE TO WATCH ROMANTIC MOVIES.
Question forms WHERE DID YOU USE TO LIVE?

DID YOU USE   TO HAVE LONG HAIR?

FOR NEGATIVES, USE DIDN`T USE TO.

WITH QUESTIONS, USE THE AUXILIARY DID.DON`T FORGET THAT AFTER THE PAST AUXILIARY DID, WE USE THE INFINITIVE USE NOT THE PAST FORM USED.