I called Disney yesterday to check for a code and I don't have one. I was told by the second CM they are not suppose to check anymore, but she did it one last time for me. I had another CM (first call) say no and that unless you got a pin code by e-mail, etc. there was nothing she could do. I tried again and I got a nicer CM. There's no way for sure to know if a CM is indeed looking for a code for you, either even if they say they will try. Obviously, if you get one that way then you know they tried for sure.
With the nicer CM I asked if there was anyway for me to increase my chances of getting a pincode and she didn't have an answer aboit it.
The only time I received a postcard pin code was one year that I took two trips. I don't know if multiple trips in the same year got me on a certain mailing list; who knows.
I did hear a while back that taking surveys at the Disney parks can help. You usually see this being done near the entrance/exit areas. This hasn't been mentioned too much as of late, here. Another way is to register for your birthday free pass. It seems quite a few who do this get an offer for their month or the week of their birthday for a 40% resort discount. That's as good as it gets basically for a resort discount. You increase your chances by registering everyone in your family for their birthdays.
Being registered on as many Disney sites as possible supposedly does help. The Disney Visa card is probably the best way to get a discount for most; at least this was true in the past. I'm hoping a Disney Visa offer will come toward August for the winter time.
I did start a post here asking those who got a pincode for December time to please share where they live. I don't know how to link it here, but you should be able to find it.