strange lighting, problem with normals? I'm trying to create a simple human mesh. While working on the torso, I noticed some shading errors. They look even worse when you move the camera around.

The one on the left is with shading set to smooth and subdivision set to 5 on basic, the one on the right is shading set to flat, and no subdivision.




Here's another one...



I've found that I can replicate the effect by simply making vertices go into the mesh.



Does anyone know how these could be fixed?
As you  have discovered, this can be caused by non-planar faces.
Ngons are particularly susceptible to being non-planar, but this can happen to quads too.

You can fix these automatically by selecting everything (A), then pressing Split non-planar faces in 3D view > Header > Mesh > Cleanup: