There's no real way to sign up. They're completely random. They say you increase your odds by registering online, and saving a few random trips you're interested in taking and then you sit back and wait. I did this last year and received three PIN codes via email. Saved me about $700 off the rack rate. But, I know others who have done this and never get PINs. Good luck!
I had a dream last night that Disney released free dining and I wasn't able to get online to book it. When I tried to call, my phone died.
I hope they release something soon....my sub-conscious can't take it