Focus on one store when you begin, because each chain has different rules, and it might be hard to keep them all straight at first. Sign up before you shop, and be sure to research the rewards programs for CVS, Rite Aid and Walgreens to find out how each program works and how to redeem your rewards.
TIP: Sign up for e-mail updates. Register with the chain to receive additional promotions, like $5 off a $25 purchase, by e-mail. Such deals can save you a bundle when combined with other discounts.