Are you talking about a current limiting resistor from arduino to the signal pin of the MOSFET? If so, why? I thought the input resistance was huge.
If you mean on the output, I'm actually running some LED strips which are already set up to take 12V raw, so the MOSFET just switches the power supply directly to the strips. Is that all ok?
Also, am i right in saying that the MOSFET is either on or off? if i put 1V on the input pin (they are logic level MOSFET's by the way) they will be off, right?