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One thing I didn't see mentioned in the helpful posts, is learning the "orientation" of your rig. In a class A, you are sitting on top of your front axel or just ahead of it. And, you are sitting at a point further above the road surface. Find a parking lot with a long straight line painted on the surface, park with the tires at the edge of the line, then while sitting in the drivers seat identify a spot on the bottom edge of the windshield where it lines up with the painted line. This will give you an easily identifiable "maximum to the right" when driving straight before hitting the shoulder. Then do the same for orienting on curves. These two spots will help you keep it on the road. It takes a steady hand, some time, and practice, to learn about where you are sitting when driving the big rigs.