retrolefty:
zenwebb:
Is a series resistor required (or good practice) on the gate?It's commonly used, not because the mosfet requires it but because the current flow when switching from high to low or low to high discharge and charge the rather high gate capacitance typical of power MOSFETs can tax the driving circuit in your case the arduino output pin. Once the mosfet is fully turned on or off no gate current is being consumed. A 200 ohm series resistor should protect the output pin well enough.
Lefty
You can't stop there, you have to tell him the rest of the ugly truth. 
He doesn't want to arbitrarily pick a very high value resistor to put between the pin and the gate. The turn on time would be severely impacted making for much more heat dissipation than would have been expected based upon datasheet calculations. IOW, turning the switch on and off slower generates more heat.