Many shoppers may be unaware of Amazon.com's Post-Order Price Guarantee.

It varies by retailer, but you'll likely find very few stores will price match Internet prices, particularly from sites that maintain solely an online presence. Some stores may not even match their own Internet prices. Doesn't mean it's not worth price comparison shopping on the fly, even if it means leaving the item behind vs haggling. You can check prices on millions of items from more than 11,000 retailers on your cellphone at wap.aol.com/shopping.

In the case of Walmart, they do not honor pricing from Walmart.com. But both Circuit City and BestBuy say they will match prices from their web site, providing the same item is in stock at a store near you. And if you buy online and a few days later see the item available in-store at a lower price, you may also have some recourse there.

When items are marked "online only" or "web special," it's spelled out pretty clearly, they're probably not going to honor the same price in store – and may not even have the item in stock at your local store. If you're a really good haggler, you might be able to work some magic, but don't count on it.

According to a recent New York Times article, on stocked items "Most store policies on bargaining are informal. Some major retailers, however, are quietly telling their salespeople that negotiating is acceptable."

Do your homework. Compare prices at multiple stores and check for online deals before you buy. Start your search on a comparison shopping site, find your bargain, print it and take it to the store as evidence to support your haggle. (Make sure it's an apples-to-apples comparison – in other words, it has to be the exact product they have in-store).

Again, mobile comparison shopping tool can work to your advantage, allowing you to compare prices on millions of products via your cell phone, while you're in the store. Try showing the results on your cell screen to the salesperson ... it may move the needle in your direction.

When haggling, if you're dealing with a salesperson who works on commission, you're likely to have more success – or plan B, find a manager who has sales goals to meet.