If you've ever used a coupon to make a purchase you are part of the 94% of adults who have made couponing so prevalent in today's society. What is surprising is that when most shoppers encounter a bad coupon online or in the store, they just buy the item at full price!

A Harris poll commissioned by CouponCraze.com, a deal and coupon collection website, revealed some surprising insight into consumers' behavior. While close to 100 percent of shoppers use coupons in the store and online;

• 72% of in-store shoppers will make the purchase even if the coupon is declined.
• 57% of online shoppers will make a purchase if the coupon is declined.

In case you missed that, more than half of the consumers will buy their item despite a price increase caused by a bad coupon code. With an average of $29 in coupon savings on a $151 bill, completing a purchase without a coupon can get expensive quickly. Even a few bad $1 coupons at the grocery store will hurt you in the long run.

This isn't just a bad idea because of the lost savings at that retailer but when you're use a coupon for electronics, as 46% of shoppers do, buying your item despite a bad coupon can also mean a bigger waste of money. There's a good chance that you ignored cheaper options when settling on the retailer offering a coupon. As painful as it is, if a coupon is declined, your best bet is to start your search from scratch.

When it comes to smaller items like groceries, continuing with a purchase even after a coupon is declined will, in many cases, result in you buying a product you wouldn't have otherwise bought. This wastes money. There's no shame in asking the cashier to remove an item because of an invalid coupon, so unless you regularly buy the item anyway, leave it with the cashier.

Personally I can't tell you how many orders I've abandoned over the years due to invalid or expired coupons. Because many of the best deals come from coupling a just-about-to-expire coupon with a barely started sale or price cut, I've probably abandoned more online shopping carts than most people have ever started. On the flip side, I can count on one hand how many times I've continued with a purchase after a coupon code failed. Heck, if I did count it's likely that I'd end up being obscene or throwing up a peace sign.

So how can you avoid overspending due to bad coupon codes? Coupon Craze offers 3 tips to make sure that you find reliable coupons and don't miss out on savings.

1. Use online coupons instead of printable coupons. If you do come across an expired or faulty coupon, you are more likely to find a replacement coupon online than if you are at the store in a checkout line.
   
2. Make sure the discount is applied to your total before you make the purchase – a discount will NEVER appear after you have purchased an item.
   
3. Avoid using sites that let users post coupons because the chances are much higher that the coupons will be faulty or expired. Instead use sites like Coupon Craze, which ONLY post coupons that are approved by the merchant.

These are all good tips to follow and while I've scored many of my biggest deals using coupons that weren't "approved" by a merchant, but unless you know what you're doing and can walk away from a transaction, you're better off going with merchant-approved and provided coupons.

When you go looking for reliable coupons you can check out sites like Coupon Craze, which works with retailers to get valid discounts as well as other sites like RetailMeNot.com. Still want to know more about coupon codes, be sure to read WalletPop's secret agenda of coupon codes.