There's a really complicated how-to out on www.jdmfan.com (when it's up).

I have my headlights wired the 'JDM way'. I just cut the wire that goes to the dim filiment in my corners and rerouted them to go to my city lights. Now, when I turn on the parking lights, I get city lights, tails and license plate lights. When the turn signal is enabled my front and rear corners, and sidemarkers illuminate.