Directories would refer to any type of record similar to a telephone book. City directories are the most common, but there are also farmers directories, business directories, telephone directories, trade directories, school yearbooks, alumni lists, and more. Each can be a valuable resource to genealogists as due to Ontario's privacy laws most records are unavailable to the public for 50-100 years. Directories are not subject to privacy laws!
Directories can be used to establish that your ancestor lived in a specific area during a specific time. They can also be used to indicate when your ancestor may have died or moved to a new location. Did you find them every year from 1891-1899 but not in 1900 or 1901? This may be a clue to look for a death record or another location.
Other uses of directories includes the history of a specific property - who owned it, who lived there, when the building on it was first built, what uses the property has had (was there a business there at one time?).
You should have two things at hand before setting about on a search for your ancestor in a directory:
1. Time - You likely have in mind the years that your ancestor lived (birth - death) but if they lived to be 80 years of age, should you really look at directories for all 80 of those years?
City & Rural Directories - Your ancestor likely lived at home until they were 18-21 years of age, until they moved out on their own you won't find them listed. With female ancestors until the 1900's you likely won't find any listed unless they were a widow or divorcee. There are some directories prior to 1867, but most were compiled after 1867.
2. Place - Where did your ancestor live during the time period you're seeking a directory? If they lived in more than one place during their life, you should check the directories of all those places. Also take note of if they lived in a city or a rural area. If they near a big city, but not in it, they might not be in the city directory (check the rural directory). But if they lived in a smaller city or town, the directory may include rural areas.
Business & Trade Directories - What age would your ancestor be likely to start, or be partner in, a business or trade? Looking for them before the age of 18-21 or after the age of 65 is not the best place to start.
Farmer's Directories - This one could be tricky. If your ancestor worked on the family farm they might not be listed until they inherited (if they did) the farm. Again, looking for them prior to the age of 18-21 will likely prove fruitless.
Telephone Directories - The telephone wasn't invented until 1876, the first telephone exchange in Canada didn't open until 1878 (in Hamilton, Ontario).
Yearbooks & Alumni Lists - Most yearbooks are for high school and college/university years, so you'd be seeking your ancestor in their teens and/or early twenties. Alumni lists are generally for college or universities and may list your ancestor from the time of graduation to the time of their death.
When seeking a directory also keep your eyes open for atlases and gazeteers. Some of these would also include the names of residents along with a biographical sketch of the area (the Historical Atlases published 1876-1878 are a prime example of this).
Start with the table of contents and introduction. The introduction will explain the abbreviations used throughout the directory.
City directories are usually organized by address. Therefore you may have to peruse each page of the directory to find your ancestor unless the directory you're looking at has an index (check the back of the book / end of the microfilm; table of contents).
Telephone directories are organized by surnames or by place then surnames.
Yearbooks are usually organized in one of two ways - by surname, or by class year (faculty, ninth grade, tenth grade, etc).
Farmer's Directories are also usually organized in one of two ways - alphabetically surname or by location (name of the township, town or village) then surname.
Business & Trade Directories can be organized alphabetically by surname, or by trade/business then by surname.
Regardless of the type of directory you find, always start at the beginning. That is usually where the editor, publisher or author placed the information regarding the organization of the directory.
City Directories: Name, Address, and occupation - usually just of the head of household. City directories also included business advertisements, listings of businesses, post office rates, a gazeteer, pretty much any information about the city the editor might think to include.
Farmer's Directories: Name, Location (Lot & Concession), Nearest Post Office
Business & Trade Directories: Name, business/trade, and location of their business/location
Telephone Directories: Name, address, phone number
Yearbooks: Name, grade, some would include anecdotes or accomplishments.
Alumni Lists: Name, year of graduation, current or last known address, current or last known occupation, some include a mini biography.
If you have a scan of an Ontario directory, please consider sending it in to be included as an example.
The National Archives & Library of Canada: The book Canadian Directories, 1790-1987 will tell you what directories the National Archives and National Library have available in their holdings through inter-library loan (see links & books below).
The CIHM (Canadian Institute for Historical Microreproductions) has microfilmed some directories that are available for purchase and through inter-library loan (see links & books below).
The Archives of Ontario: Also has a collection of directories from across the province available for loan on microfilm.
Archives: Check the area where your ancestor lived for an archive. Most won't loan their materials but they will allow you to visit (or have someone visit on your behalf) to look at the directories. Some archives will do a lookup for you for a fee (others are too small or understaffed, so hiring a researcher may be your only option).
Libraries: Same as archives, but also be sure to visit your own local public, college or university library (all three if you're that lucky!), you never know what they have in their holdings or what they can request through inter-library loan.
LDS Family History Centres (Worldwide): As the CIHM has microfilmed several directories you may be able to access these through a Family History Centre
Finding Ontario Directories online is hit or miss. There isn't an organized effort to bring any of these records online. Directories known by OntarioGenWeb to be online are linked below.
Books (Biographies, Local Histories)
Questions & Answers