I started out on this with Walgreens after seeing the http://jane4girls800dollarannualbudget.blogspot.com/ one time. She mentioned having 9 items rung up at a time. There were so many items offerred with Register Rewards that I knew I would use eventually, that I haunted several Walgreens stores and that first time wound up earning $160.00+ in Register Rewards that week, then spent that on items that would earn rebates, and helping a friend get started. I watch for the $5 or $10 off one day only (always Friday) Walgreens coupons that are usually posted on the Walgreens thread. I have rebates on a gift card, and those are helping me buy next month's rebate items. Walgreens will take their own plus manufacturer coupons, but the Register Rewards can't be spent on items to generate more Register Rewards.
At the suggestion of a fellow Forumite, I have also been working the CVS deals, but am still not proficient with those. Many of the items are already gone from the shelves when I get to the store, and I look up ads in advance on Hot Coupon World for some of the stores.