this is mostly a going back over the other replies, yes inform your bank of your travels so they don't freeze your cards, when using ATM's look for the Interact and Plus logo's on the back of your card, and the ATM's ( US = Plus , Canada = Interact). Discover cards are far and few between here have a back up.
Know your Pin number for your CC , bank cards, as you will need it to do anything. forget the checks both normal and travelers, they will not likely be accepted in Canada.
Fuel prices expect to spend 30% more ( diesel 1.33 a Liter, Gas 1.03 a liter and its way down here, was 1.35 ) now that said, in BC Canada, its now Law you must Pre-pay all fuel, if you don't know how much they just put a hold on your card and charge actual no need to go back inside.
if you normally carry firearms, bear spray , mace, better check first as you likely wont get across the border.
Pets have there license's up to date along with shots and records on hand.
think that's it, also know that double tow's are illegal in BC as well, so no pulling your RV and boat.
your Wal-Mart = our Wal-mart
your Harbor freight = our Princess Auto with a lot less cool stuff.
and forget our Target stores they share a name that's it.