Any help is appreciated!http://lmgtfy.com/?q=arduino+relay
Really - is it that difficult to figure out? Now, of course, that'll get you the "how", but the what is slightly more complicated: You basically need to know some specifics about what kind of load you are switching. You say it's a "12 volt" switch; so does that mean the load is really 12 volts? If so, then what kind of current are you looking at? If you don't know the current, then anything about watts? At any rate, once you have a figure, then you need to figure out the current, so you know what kind of contact rating you need for the relay. If we are talking about an automobile circuit, though, then a simple SPST Bosch relay rated at 40 amps or so, while it might be overkill, is fairly dead standard, and can be found at a junk yard.