used to do - be used to doing

This is to draw your attention on the difference between two closely related structures: used to do something and be be used to (doing) something:

You use used to do sth to talk about something that happened regularly or was the case in the past, but is not now: I used to smoke, but I gave up a couple of years ago.

Except in negatives and questions, the correct form is used to: I used to go there every Saturday. To form questions, use did: Did she use to have long hair? Note that in negatives and interrogatives the correct spelling is use to, not ‘used to’.
The negative form is usually didn't use to, but in BrE this is quite informal and is not usually used in writing.
The negative form used not to (rather formal) and the question form used you to…? (old-fashioned and very formal) are only used in BrE, usually in writing.

You use be used to sth/to doing sth to talk about something that you are familiar with so that it no longer seems new or strange to you: We're used to the noise from the traffic now. • I'm used to getting up early. You can also use get used to sth: Don't worry — you'll soon get used to his sense of humour. • I didn't think I could ever get used to living in a big city after living in the country.