[bread_baker]

What ages are your students?
I'd explain that "used to" can be used for a past habit or condition that is no longer true.
Examples: She used to eat desserts. (Implying that she doesn't do that anymore)
There used to be a Chinese restaurant on this street.
Amy used to date my brother.
Peter used to live in New York.

I'd write a lot of examples on the board and carefully explain the grammar. In my class, I like to have students write with the new grammar before they speak with it. You may find exercises for this grammar in a good grammar text.
I'd definitely try one or more speaking activities with this grammar. Choice of activities will depend on the ages of the students.