Well, a lot of the smaller, more remote, or less popular areas which are still great camping sites do not have visitor's centres like the main ones do. So I don't think anyone would track you down if you didn't pay... With that being said, if you are going through British Columbia a good resource would the BC parks web page:
http://www.env.gov.bc.ca/bcparks/fees/
For the popular camp sites you will generally find that there is a fire pit prepared and an area where branches have been cleared for a tent and maybe even some logs for seating. This is just from so many people using the common area. If you go off into the crown land like
@Northern Dancer suggested then you might have to hunt a bit more to find a nice spot and it will be more remote but also you won't need to pay any fees.