If I have 6 led lights at 2 volts each will I still have to use a resistor on a 12 volt system and how would you wire it up?

Led's have variety of voltages, try this calculator:
http://www.bowdenshobbycircuits.info/led.htm
There is also a formula where you subtract the led voltage from the source voltage then divide the ma's into the voltage difference.
Helpful when you don't have a computer handy.