Wow, I found a pretty awesome deal, though it's ymmv. Went grocery shopping at HEB (a chain of grocery stores that I believe are only in Texas) yesterday, and bought four 12-pks. They usually give you coupons and stuff when they give you your receipt, and one of the coupons was for 30 free points!
The coupon specifically says 'Congratulations! You're eligible for Double Points,' meaning you get it for buying three of the 12-pks. That's pretty good, since they're currently selling at 3 for $10.