Census returns can be a treasure-trove of information as they record the entire household at a given address along with their occupations, the relationship to the head of the household and their place of birth. While censuses have taken place every ten years from 1841 (with the exception of 1941) there is a one hundred year closure period on these records so those that are available span the period 1841 -1901.
These are available on microfilm and are held at all the main libraries and at the Aberdeen & North-East Scotland Family History Society. All local Registrars also hold digital images of census records and again, you can access digitised versions online at www.scotlandspeople.gov.uk.