I'm guessing that you're looking for a job in Europe, because that's the only place where the term "park shaper" is used.
In contrast to what someone said above, being a good rider does not have much to do with being a good shaper, although it certainly helps. You should know how every kind of feature should be shaped, and preferably be able to ride it yourself to make sure that what you build actually works the way you wanted it to.
More important than this, though, is the physical and mental strength needed to perform manual labor for long periods of time, in all imaginable weather conditions, usually for a wage that's laughable.
I won't lie, being a shaper is a fucking great job, but it's not all fun and games, and if you're not interested in hard work, especially when everyone else around you is having fun (like shoveling out the park on a pow day), then it's not for you.
All that said, QParks is a good option to check out if it's your first season and you don't have any connections. Without experience or connections, it's really hard to land a job in the park.