This link on our LearnEnglish Teens website is about 'used to' to talk about habits in the past:
http://learnenglishteens.britishcouncil.org/grammar/intermediate-grammar/used
This is from our LearnEnglish website, and it's about 'used to' and 'would':
https://learnenglish.britishcouncil.org/en/intermediate-grammar/past-habit-used-towouldpast-simple
This one is about the difference between 'used to' for past habits and 'used to + -ing' for things you are accustomed to:
https://learnenglish.britishcouncil.org/en/intermediate-grammar/used-infinitive-and-beget-use
Don't forget to look at the grammar file at the back of your student's book, too! Pages 160-161!
