panman,
I gathered that it's easiest to live trap them, and I've read that they love salt.
Here's a paragraph from an article I found:
Porcupines have a taste for salt, succulent plants, fruits, vegetables,
tool handles, wooden wheel barrow handles, boat oars,
porch furniture, toilet seats, saddles, tires or anything else which may have had salt on them. Wooden tool handles absorb salt from sweat which is certain to attract feeding porcupines. Any automobile which travels on salted roads in the winter will be absorbing a lot of this mineral which will lure porcupines to feed on the tasty tread.
The article also said that they usually have a large range and only stay in one spot until they exhaust their food supply. Hope this helps, and good luck!!