A census can be an amazing source of information including age, birth date, marital status, religion, occpation and country of origin. It's also easy to obtain free access using easy genealogy research tools and tips. If you're not sure which County or District your ancestor lived in, try a general search then narrow it down as you gather more information.
Headings vary so read carefully. Census might ask for current age or age on next birthday. Census-taking dates vary too which impacts the calculated year of birth.
The 1901 census includes full birthday and year arrived in Canada, very useful information for future searches.
Heads up on names. Many early immigrants were illiterate and had their own ideas of how a name should be spelled (or none at all and made it up). And heavy accents of Householders also impacted the way names were heard by census-takers. I found one where the name Benson was written down as Vincent. Also, the quill-writing back in the day was quite fancy-dancy, compounding the variation problem for transcribers. Silly, Jilly or Tilly? So make good use of the wild-card search option if your name, as it is spelled now, doesn't pop up.
WHERE TO FIND A CENSUS
Government of Canada Library and Archives (LAC) has over 16 million records in its searchable database including Immigration, Land Petitions, Military and Census. Search results are categorzed by type e.g. immigration and decade which helps to cut down on hits. It's a good idea to browse the site and familiarize yourself with the general family information available. Search and download are free.
Military records are a useful tool for next of kin, address and physical features like hair colour and eyes.
Automated Genealogy site offers a free searchable database. Location is not needed for your search if you're unsure where your ancestor lived. Simply narrow the hits as you view them. Original census images are also available except for 1852 when original census forms were destroyed or lost. Sad. SEARCH
If for some reason, you can't find a census, they are on microfilm at the Ontario Archives (York U campus).