1. Make sure your model is manifold and free of self intersecting surfaces. If there are errors, you can typically solve them quickly by importing your model into Microsoft's 3D Builder application and then saving it again.
2. Make sure that if you're attempting to print sections that are thinner than your extrusion width that you have turned on External Single Extrusions in the Thin Wall settings area of the Advanced tab.
"A bird does not sing because it has an answer. It sings because it has a song."