I am fairly new to CVS'ing, but I'll attempt to explain it. Yes, you need to sign up for an extra care rewards card (which is free). Each week, check CVS' ad to see what items (or combination of items) will earn you extra care bucks (ECBs). (I usually check here and other websites for a preview of the ad and coupon match-ups to plan my trip in advance.) Purchase items that earn ECBs. The ECBs will print at the bottom of your receipt. Clip 'em and roll them by using them to purchase other items that earn ECBs. The best part is that ECBs are earned prior to any coupons being applied to your purchase. So, say for example, CVS has Colgate toothpaste in the ad for $3.79, but you earn $3.79 ECB. You also have a $1 off coupon for any Colgate toothpaste, which you use. This brings your out-of-pocket total to $2.79, and you've earned $3.79 to use for your next trip. CVS has just "paid" you to take toothpaste off their hands.
Many CVS stores also have red coupon machines. Mine only recently got one. As a pp mentioned, when you walk in, scan your card at the machine and it will spit out coupons. A $3 off of $15 coupon will usually print out for me on a weekly basis (either at the machine or at the bottom of my receipt).
I will note that CVS' prices are typically higher than Target or Wal-Mart. The key is in earning those ECBs. The best example that I can give is say, for example, CVS has soda on sale 4 12-packs for $15. Target might have the same soda on sale for 4 for $12. At first glance, it appears that Target is the better deal. But, I almost always have a $3 off of $15 coupon for CVS. I apply that and it brings the total at CVS down to $12, matching Target's price. But, then on top of that CVS has a deal where you spend $15 on soda, and you get $5 ECB. Since ECBs are earned before coupons, I am now paying $12 out-of-pocket for soda, and walking away with $5 in my pocket for my next shopping trip. CVS now becomes the better deal.
As another example, last week I got a box of diapers, 2 boxes of Gerber cereal, 3 12-packs of soda, 2 2-liter bottles of soda, 2 16-packs of Charmin, and a 20 pack of batteries all for $30 out-of-pocket. (I did this in multiple transactions, rolling my bucks.) I walked away with $8 (ECBs and a coupon for my next trip). On a normal day, I *might* be able to get just the diapers and the 3 12-packs of soda for $30 at Target or Wal-Mart. So, I essentially got the cereal, Charmin and batteries for free.
At first, I was skeptical, but now I'm a big fan of CVS. I hope that helps!!
