Start at home and look for clues and leads. Look around you. Go through those old photo albums. Check family books or accounts for notations of marriages, births and deaths. Talk to your grandparents or other relatives. Sift through a trunk that is filled with old letters and deeds.
Organize your project. Chart everything that you already know about your ancestors (names, residences, professions, dates of birth, marriage and death). Work from the present back to the past. You may want to read a few introductory books on how to do genealogy research.
Explore the records. With the help of reference archivists, identify the resources at the Archives of Ontario that will help fill some of the gaps in your research.
Begin the adventure. Remember to keep careful records of everything you found and where you found it. Keep track of specific reference codes or microfilm reel numbers as you may want to go back to check something. As you work with the records and gain experience and knowledge, you can gradually expand your investigations. You may even plan an overseas trip to investigate similar collections in other countries.
Read all about it! As you work, try to supplement your investigations through targeted reading. For example, if your great grandfather was an Irish immigrant who became a fireman in Toronto in the last two decades of the 19th century, you can search the libraries for general works on Irish immigration to Ontario, the history of fire-fighting in Canada and general social histories or books on the urban geography of Toronto.