mccauley, the reason behind wiring in parallel is that you will have the same voltage across all fixtures. If you were to wire in series, the first fixture will have the proper voltage, say 12V, then the voltage will start dropping with each additional fixture on the circuit. In other words, the 1st fixture will have 12V, the second might have 11V, then the next one 10V, and so on. This means that your fixtures will be dimmer that the previous one on the circuit, with the last one on the circuit being the dimmest.
Sailingdog comment is based on wanting 12V at the very last fixture, so you would have to raise the voltage at the begining and have some blindingly bright & hot lamps
. As he said, this will also consume more amps.
When wiring in parallel, you take the positive wire and connect it to the positive terminals of ALL fixtures on the circuit. The you take the negative wire and connect it to the negative terminals of ALL fixtures. In the end, you will have one positive and one negative wire going to your fuse, for each circuit.
This would be a series circuit, and like I said, voltage would go down from 12V at the first fixture, and go down with each additional fixture.
Also, in series, depending on the fixture itself, if you turn off a fixture (you are opening the circuit), the rest of the fixtures on the circuit will go off. Sort of like the older Christmas lights, that once one goes bad, the rest also turn off. However, there are ways around that with fixtures designed specifically for series connection.
I agree with sailboy, I would go with one stardboard and one port circuit