In order to make the most of the deals at CVS the first thing to do is to sign up for a rewards card. It's completely free and will qualify you to receive extra bucks and other deals.
Each week CVS has various deals where you can earn "extra bucks". These are in essence money back for buying a particular product. They come in the form of a print out at the end of your receipt which you can use as money to buy other items at CVS.
For example this week Re-nu eyedrops were on sale for $7.99 with $7.99 in extra bucks or ECBs. You pay $7.99 and CVS gives you $7.99 back in ECBs to use on another product essentially making it free.
You can make this deal even better if you have a coupon for money off the item you are buying. For example if you had a $1 off coupon for the Re-nu eyedrops then you would have paid $6.99 and received $7.99 back in ECBs earning yourself one extra dollar.
Take a look around in your local CVS and you'll see the magic coupon machine. If you scan your card, it will give you some coupons off various items. About once a week or so it will give you one for $4 off a $20 purchase. This combined with ECB deals can make for some pretty great deals.