Look at this sentence:
I used to live in London.
“used” + infinitive describes a habit, action or state in the past that is no longer true in the present. In this example, the above sentence suggests that I no longer live in London in the present.
In this lesson, you will learn the form and also more examples of how to use this structure.
Form
affirmative
subject + “used” + infinitive form of verb
(The infinitive form of a verb is the word “to” + the base form.)
I used to play
you used to play
he / she / it used to play
we used to play
you used to play
they used to play
This structure only has a past form:
I used to play football. 
There is no infinitive form of the verb “use” in this structure:
I am going to use to play football. 
There is no -ing form of “use” in this structure:
I am using to play football.
There is no present form of “used” in this structure:
I use to play football.
To describe a habit or regular action in the present, we use the present simple:
I play football every day.
Negative form
subject + “did not use” + infinitive form of verb
I did not use to play
you did not use to play
he / she / it did not use to play
we did not use to play
you did not use to play
they did not use to play
Negative contracted form
We use the contracted form in informal spoken English.
did not -> didn’t
I didn’t use to play
you didn’t use to play
he / she / it didn’t use to play
we didn’t use to play
you didn’t use to play
they didn’t use to play
Question form
did + subject + “use” + infinitive form of verb + “?”
did I use to play?
did you use to play?
did he/she/it use to play?
did we use to play?
did you use to play?
did they use to play?
We can also form a question starting with a question word as follows:
“What”
“Where”
“Why” + did + subject + “use” + infinitive form of verb + “?”
“Who”
“How”
Examples:
Why did you use to walk to work?
Where did they use to go at the weekend?
What did you use to eat for breakfast?
Use and meaning of used + infinitive
Habits in the past
used + the infinitive to describe a habit or regular action that we had in the past. We do not have this habit or do this action in the present.
Examples:
Jane used to smoke.
(She no longer smokes.)
Sarah used to jog every evening after work.
(Now, Sarah prefers to relax every evening.)
States in the past
used + the infinitive to describe a state that we had in the past. We do not have this state in the present.
Examples:
Mark used to like rock music.
(Now he likes classical music.)
Mark used to be a chef.
(Now he is an electrician.)
Mark used to like hamburgers.
(Now he prefers fruit.)
Other lessons
Present perfect verb tense
Past simple tense
How to use DO and MAKE
IELTS exam day from start to finish
