MODDING 101: LEDs MADE SIMPLE
 

A typical LED will have a long pole and a short pole. The long pole is the anode or positive side, the short pole is the cathode or negative side. Some LED manufacturers have poles of similar size or you may be using a used LED, in this case there might be a flat side to the acrylic on the negative side. If there is no flat side and both poles are of same length then look for the “cup” that is also the negative pole.

Direct Link: http://www.casemodgod.com/leds_and_modding.htm

I made a series of the same hook up several months ago. Should have told JMke or write the how to article on the same topic. Anyway, it is a good article; you should try it.;)

Another way is do it is to use 5V LED lights, which does not require the use of resistor. I use a piece of plywood and nails to pre-route the wiring harness, making soldering easy. The connector I use is the common 4-pin molex using the 5V lead.