Canada's Wonderland is by far the best theme park in Canada. There are massive roller coasters, the most popular being Behemoth and Leviathan. The drops for both of these are ridiculous so if you like a rush of adrenaline, this is the place for you! But don't fear, if you don't like roller coasters there are many other rides so you will not be bored. I love the water park in the summer which is also huge.
In terms of how you pay, you can either buy a pass or tickets which gives you full access to the park (except the theatre I believe). Weekends in the summer have longer wait times on rides and the front, so come early either way! They check you at the door, you get stamped and you enter with a gorgeous view of the Wonder Mountain.
My favorite part of going there is definitely the funnel cake which I never miss. You also have endless choices including pizza, hot dogs, Manchuwok, etc. Do know that these are a little on the pricey side. Be prepared for a day of lots of walking and fun!