Here are the links to store coupon policies. Make sure you print off a copy of each before heading to the store. You want to make sure you are familiar with each store's policy to avoid confusion and frustration during your checkout!
Stop and Shop http://www.stopandshop.com/customer_service/faqs/index.htm?q=shopping
Market Basket/ Demoulas http://nesaving.wordpress.com/demoulasmarket-basket-101/
Rite Aid http://content.riteaid.com/stores/CustomerCouponAcceptancePolicyAugust2010.pdf
* Please keep in mind that these coupon policies may change at any time. Check them every few months to keep yourself up to date. There's nothing more frustrating than going to the store to find out that their coupon policy has changed!