Rally school is not strictly necessary, but it'd certainly help your first rally not end up like mine (176 minutes lateness penalty... wheee!

). Luckily, there is one being organized in March, running on three evenings, for I believe $50 per person total. First and last evening are classroom, middle evening is a short navigational rally practice
There are numerous online resources as well. There is a good set of instructions on
Toronto Autosport Club Website; and a set of links on
Rallysport Ontario webpage.
You should check out instructions from some of the previous rallies (for example,
Discover Ontario has a few). There is also often a quick info session for beginners before some of the rallies. Finally, come early and talk to some of the friendly folks before the rally, they'll be glad to share some tips & tricks with you

.
No matter.
You
will get lost your first rally!

Well, at least if you start with one of the
provincial ones. MLRC Mini-rallies, you stand a fighting chance

.
(After a couple of rallies, I strongly recommend Brooke's free
Rally Calculator for palm pilot. It'll confuse you on the first rally or two, but afterwards it'll ease some of the more routine tasks).