I am working on an Arduino project where I would like to use an output pin to control a 12v load with a mosfet. I think it should be an n-fet, but am not sure. I have been looking at specs, and don't know how to pic a fet that will do what I want. Can anyone point me at a part I could use?
How much current do you require? For specs you want a FET with a breakdown voltage (BVDSS) above 12V and a current rating that exceeds your load. A logic-level FET can sometimes be better but it probably will not matter if your current requirement is only a few amps. N-channel is usually what you want.
I use the On-Semi NTP65N02 with a 3.3V gate drive level for a current-sink. TO-220 package and a fairly low Rds(on) at that level.