Here are a few thing I do to make it easier and quicker at the checkout counter when i use coupons.
#1 Make sure you have your coupons out and ready for the cashier before you get to them. I usually wait out of the way in the section before the cashiers to check that I have them out. Then I double check the following.
#2 Always make sure none of the coupons you will be using are expired. No store will take an expired coupon. If it says "expires 9/27/2012" Then the last day you can use that coupon is on the 27th. It is expired the next day on the 28th.
#3 Make sure your items match the coupons you are using. That means the item size and description needs to match the wording on the coupon Not the picture. It is ok if the picture is different than the wording. Example: picture of Honey Nut Cheerios and the coupon says "off any Cheerios cereal" Then that coupon is good on any flavor / variety of Cheerios. If it doesn't state a size your coupon is good on any size they sell of the item you are getting. That is when couponers usually check the travel size section. Gotten a few free hand creams and toothpaste that way.
#4 Know your stores coupon policy. I have a printed copy of the stores policy in my coupon binder for each store I coupon at. It's important to know what stores double coupons. Also what stores may give you overages if your store allows that. You can check some of the coupon policies here. You should check them every few months in case they change.
#5 I like to know what my final price is going to be after coupons. Remember that if you will be getting a taxed item for free most of the time you are responsible for the original tax on the item.
#6 Now that you have all your coupons in hand for your items you will need to pick your cashier. You can find tips on picking your cashier here.
With all these tips you should have a smooth transaction. That means less people waiting in line for you to dig out your coupons. Less chance of needing to argue with the cashier about how you think you are right only to find out your coupon expired or there policy is different than you thought.