Go to
http://www.tc.gc.ca/aviation/general/FLTCREW/study.htm and there you can download the study and reference guide for any Transport Canada exam. Each document is a fairly detailed syllabus, and if you research each point listed, you will not be surprised by anything on the exam. Note that the Commercial Pilot syllabus is included by reference in the ATPL one, so you'll need it, too.
Everything you need for the air law section is available on the web at
http://www.tc.gc.ca/aviation/regserv.../doc/index.htm Don't try to use the site search engine (it searches obsolete sections, for some reason), instead use your browser's find on page command.
The AIP Canada is a very useful reference. I think I could have passed all my exams using it alone.
Get a hold of some Canadian charts if you're not familiar with them. Charts vary from country to country.
If you're not from Canada, pay particular attention to the aspects of weather that are different here than where you are from. Know critical surface contamination, cold weather adjustments to published altitudes, and local style tweaks on FAs and TAFs.
Good luck. Tell us how it goes.