Finally...

Finally get the picking done. It seems to work well. The problem I had was putting gluPickMatrix inside GL_PROJECTION matrix mode and before gluPerspective. It's funny how they usually don't mention this type of calling sequence in the obvious place in the book etc. I only found this out in Lesson 32 of NeHe production example code. Without knowing the details of the function it's hard to evaluate what the problem is. But it's a good lesson about OpenGL.
Now I will have to start the next phase, which is...how am I going to add in a tile etc?