Basically you want to make sure Disney has an e-mail address on file for you. I've heard that they send out snail mail cards as well, but I've never seen one.
I've gotten a few pins over the last couple of and most of them I haven't been able to use. I think what triggered the most recent one for us is the fact that we had a trip planned and booked, and then canceled it.
When I had a trip planned and a deposit made I didn't receive any pins.
You basically want Disney to know that you want to come. If they think they can get you there extra, they'll try.
- ordering planning DVD
- opening a Disney vacation account
- "planning" pretend vacations
None of the above guarantees that you'll get a pin, or that the pin you'll get you'll be able to use, either because of dates or because there's no availability in the resort and room you want. A lot of people have gotten frustrated because they get a pin and try to apply it to an existing reservation and are then told that it can't be applied, because there's no availability for their particular room.
Codes are available for public use, and are usually a set of three letters that you tell the CM when you book. Availability is just as if not more restrictive for general public discounts, and the discounts usually aren't as good.. For next December a deal will probably be released some time in the Fall, usually mid-August, though this year they were released in July.
You can look at this site for the release of past discounts. They only list the type of discount, not usually the amounts.
http://www.mousesavers.com/historicalwdwdiscounts.html
There are usually code watch threads on these boards for particular time periods.