He isn't doing a signing tour for TGO, and he doesn't do private requests. He does, from time to time, appear publicly and do signings, but they are rare and not generally conveniently located. You'll be hard pressed to get a signature on your own, and there are only a few signed copies floating around ebay. I have no advice, other than, if he's going to be somewhere, we'll be geeking out about it here.
4+ years ago I drove several hours from NY through Canada to some university to hear him do a reading. Afterwards, about 10 of the 30ish people had books for him to sign. That's the last known appearance/signing I've heard of.