Momentary Switch Wiring - Model Railroader Magazine

I plan on using minatronics Momentary 3 pole switches for the 12 switches we have.

SO I get the two outer positive and negative wires...they control which way the switch is thrown. What about the common wire?

I understand it daisy chain's through each switch but where does it begin and where does it need to end? Does it need to come off the ground? Or does it just connect between each saith and that's it?