We use used to do to talk about the past. It is not a tense but it is like a tense. It is a special structure. We use the structure used to do for the past only.

Structure of used to do

The structure of used to do is:

subject

+

main verb use

+

to-infinitive

Look at the structure again with positive, negative and question sentences:

	subject	auxiliary did	not	main verb use	infinitive
+	I			used	to like him.
-	I	did	n't	use	to work.
?	Did	you		use	to drink?

Used or use?

• when there is no did in the sentence, we say used to (with d)

• when there is did in the sentence, we say use to (without d)

Use of used to do

We use the used to do structure to talk about:

• an activity that we did regularly in the past (like a habit)
• a situation that was true in the past

past	present	future
I used to smoke.

Look at these examples:

past	present
She used to work in a shop.	Now she works in a bank.
He used to watch a lot of TV.	Now he doesn't watch much TV.
They used to be married.	Now they are divorced.
There used to be a cinema here.	Now there is a supermarket here.
I didn't use to go swimming.	Now I go swimming.
Did you use to smoke?

used to do Games

http://www.englishgrammarsecrets.com/usedto/exercise1.html

https://elt.oup.com/student/solutions1stedition/int_unit_page/unit2/grammar/exercise2?cc=cz&selLanguage=cs
http://www.englishgrammar.org/exercise-8/

http://www.englishexercises.org/makeagame/viewgame.asp?id=1230