Want shadows in my rederer .... where to start?

Im doing 3d renderer in VC++ (objects consisted from points array and faces array into points array with built adjacency and so on features).
But it lacks shadows.
What is the simplest and best way to do objects casting shadows in OpenGL.
(The question is that I didnt use shading language and is it simpler than doing all shadows math by hand in VC++ and there to start)