Using Freedom of Information or Access to Information requests to obtain government information can be an extremely effective - and sometimes unavoidable - research tactic.
You need to be aware of issues of time and cost, however. Some jurisdictions - Canada federally - charge a fee just to file a request. Others do not charge anything for an initial request. Some jurisdictions have a very quick turnaround time while others - Canada federally, for example - can be quite slow.
There are also rules about which information is available and which information is not. The manner in which you word your request will also affect how quickly and how accurately you get what you want.
Right To Know Canada is the web site of an extremely helpful and comprehensive guide to the web sites of Canada's federal, provincial and territorial Freedom of Information commissions.
The BC Freedom of Information and Privacy Association has information on Requesting information from public bodies. The tips and suggestions in these documents are broadly applicable to all FOI requests.
One of the best tips is to talk with someone in the relevant government unit BEFORE you generate a FOI request.