Star the items you have coupons for or for price matching to remind you at the checkout line that you need to give these special attention. If price matching, next to the shopping list item, I write the abbreviated store flyer name, page number and advertised price. When looking at the shelf price, I can easily see if it is worth doing price match just from my list and the store name and page number helps me find it quickly at the checkout. I always circle the item in the flyer with a Sharpie so I can see it really quickly. I always put these items in one section of the cart and unload them first and get it over with.
Store the coupons you plan to use in envelope.