If you're a beginner/novice, generally stick to the right of Sheppard for trails. If you're intermediate/advanced, the left is where you'll find lots of singletrack that rarely stays on level ground. There still are some advanced sections to the right of Sheppard, though. The good trails are pretty hard to find, but worth it. There's also some sections of open forest that the adventurous rider may want to DH on the right of Sheppard on the top of Snake hill. Don't come here expecting for a day-long ride though. Right of Sheppard is the busy sections. lots of pedestrians.
How to get there:
Coming from Toronto head east on Sheppard Ave. until you come to the Rouge. It's where the paved road gets really steep and curvy. There's lots of trails to take going off either side of the road. They all interconnect to each other