After projection to clip space the points will no longer be normalized. This can be restored by dividing all components of the vertex by the fourth component (w). This will (together with the projection transformation) result in that the projection volume will map to a cube with minimum corner in (-1,-1,-1) and maximum corner in (1,1,1). For example in OpenGL, the near clip plane will map to -1 ( in DirectX it will be mapped to 0) and the far clip plane will map to 1.
The division by w (homogenization) is performed automatically between the vertex shader and the fragment shader in the procedure called Rasterization.