We just came back from a jaunt north. Many rigs are headed north. It would not be necessary to make reservations, however I would start looking for campsite early. Suggest by about 3 PM. We used many provincial parks for less then $20 Canadian per night. We used private campgrounds at the major stops such as Dawson Creek and Whitehorse. Do expect much for internet!
As soon as you get into Alberta and then again in British Columbia, pick up their respective Provincial Campground brochures. They show many campgrounds, how many sites and services(if any)
Laird Hot Springs is a must stop!
Canadian Customs do like fresh fruits and vegetables. They do not like chicken products including eggs. get them in Canada!
Gas is readily available. Run on the upper end when you get farther north. Some are 100 miles plus between stations.
If you do not have a Milepost Magazine suggest you get one. Even though it is full of ads it is quite complete for fuel stops.