Vertex shader lighting

Hey,
I’m having a huge trouble with vertex shaders, everything works great for the main directional light, however I don’t get how you add other directional lights, point lights, their shadows etc. Could someone explain to me how this is done? Also, I have just one TEXCOORD left to use in v2f struct (optionally I can get rid of fog coords if one isn’t enough)

This is the best reference guide I know to writing Cg shaders for Unity: Cg Programming/Unity/Multiple Lights - Wikibooks, open books for an open world

But is there a good reason why you’re writing a vertex shader rather than a surface shader which will handle all the lighting calculations for you?