"Thanks for your thoughtful gift! Did you happen to keep the receipt?"

You may sound like a cad for asking, but without a gift receipt you could be out some serious cash when you finally make your way to the front of the "returns/exchanges" line.

This year retailers are getting strict about enforcing holiday gift return/exchange policies -- some have even instituted new rules just for the season. Customers who aren't prepared may actually lose money on something purchased at full price just days before.

So how do you make sure that you get a reasonable refund for those three extra coffee grinders and eight video games that your kids already own that end up under the Christmas tree? Here are 11 tips that will help make your holiday returns happy:

Return the unwanted item ASAP. Tighter return deadlines on holiday purchases mean that shoppers at some stores have just 14 to 30 days to return an item for its original price. Wait too long, and that lovely $55.97 deluxe mahjong set may be marked down to $7.99. And that's what you'll get in return.

Don't open that box! If you've manhandled the merchandise, you may be charged an "open box fee," which is often at the discretion of the store manager/clerk. At Amazon.com (NASDAQ:AMZN), an open CD, software, or DVD will cut your refund by 50%.

Be prepared to pay the price for unwanted electronics. Restocking fees (particularly on electronics purchases) are commonplace and can run around 15% of the item's original price.

Be flexible. You may get more to spend if you're willing to accept store credit instead of cash back.

Whip out the right card. Remember to bring the original credit card you used for the purchase if you're returning a gift you bought. If you paid with cash, you might have to wait weeks for a refund check to be sent.

Befriend the sales staff. Niceness counts. Employees sometimes use their discretion about whether to allow return/exchange transactions. Avoid peak shopping hours so employees are less frazzled and more willing to work with you. If you hit a brick wall of resentment, try a different branch.

Don't get blacklisted. Stores like Home Depot (NYSE:HD), Sports Authority, and Barnes & Noble crack down on frequent shopper-returners by limiting the number of exchanges within a certain period of time.

Turn dud gifts into green. Got a stack of gift cards for stores that aren't your style? Swap them (or sell them) for something better at sites like swapagift.com, CertificateSwap.com, and Cardavenue.com.

Sell it off. Ebay (NASDAQ:EBAY), Amazon's Marketplace, and Half.com (owned by eBay) let you hold a garage sale in any weather. If you don't want to give these folks a cut for providing a selling platform, head to Craigslist.com, an online version of the local Town Crier that offers free listings and person-to-person transactions.

Donate it. Someone else may actually like that precious needlepoint puppy bedspread that clashes with your mid-Century Modern decor. Donating it to a charity not only earns karma points, but your good deed may get you a deduction on next year's tax return. However, make sure you do it right because Uncle Sam is keeping closer tabs on noncash charitable contributions.

Regift it. C'mon, everyone's doing it -- or at least one in four of us admit to it, according to people who track such things. If it'll help cut next year's holiday tab, then go ahead and rewrap those clunkers (first make sure you remove the original card from the box) and set them free next year.

For more on avoiding holiday blunders and finding real deals, see:

Amazon.com and eBay are Stock Advisor selections. Home Depot is an Inside Value pick.

Dayana Yochim doesn't mind receiving regifted stuff for the holidays, so long as it's figure-flattering. Read more of her money-saving/money-making tips in GreenLight, where herfavorite bargain websitesappear in the November issue. Takea free 30-day trialfor access to the archives, advisor blogs, subscriber discussion boards and at least $450 worth of tips every month. The Fool has adisclosure policy.