How can I become familiar with flight rules specific to Canada when flying there from the United States?
In the specific case of Canada, AOPA and COPA have a lot of information aimed at US pilots. AOPA has a complete guide on documents, customs etc. and COPA has a page with more information, which includes this remark:


  The flying rules are almost indistinguishable - reading the COPA guide
  should keep you legal and out of trouble. Make sure you get a Canada
  Flight Supplement (CFS) and some VNCs (Canadian equivalent to your US
  sectionals), that will allow you to navigate VFR safely.   IFR plates
  are available from Nav Canada as a subscription or the (sample list
  of) vendors included below. (by mail order)


The guide is free but available to AOPA/COPA members only.