I found this site and thought it would be very useful to many, enjoy! http://www.bcae1.com/relays.htm
here is another i use alot... has easy diagrams just click on the options at the bottom.. http://www.the12volt.com/relays/relays.asp
I use one for my fuel pump on the car. I am going to do the headlights too so I can get alt voltage and keep the switch cool because it will just trigger the relays(high low beam) . Great stuff.