(MONEY Magazine) – In many a holiday home, atop the growing mat of needles from the Christmas tree, there's a pile of gifts to be returned for another size or color, or some other item entirely. In fact, 11% of all goods sold by department stores this year will be returned. But more stores are making it more difficult to trade in items that might have been used--or at least tried out--like consumer electronics and evening gowns. So if you have visions of crowded malls and no receipts, you may be considering just hanging that third cuckoo clock out in the toolshed.

But wouldn't you rather have something you'll use? Doesn't the giver want you to be happy? Don't savvy merchants wish to keep you as a customer? Our timely advice will help you get what you desire.

--Don't throw away the box. Keep the original packing materials and instructions, especially for appliances and electronics. The retailer is more likely to honor the return if it can recognize the item as its own and repackage it.

--Help the store learn the price. If your present didn't include a "gift receipt," which hides the price in a numerical code that allows a retailer to punch up purchase details, take a chance and ask the gift giver for a receipt. (It's easier if he or she is a close friend or relative or if it's simply a matter of size or color.) If the giver has no receipt, ask for the date of purchase and method of payment. The store might then be able to trace the transaction and give you full credit. Otherwise, "You're probably going to get a sale-price credit and not the original purchase price," says Elysa Lazar, president of Lazar Media, a publisher of smart-shopping books and newsletters.

--Remember, the early bird gets the return. Don't wait too long to make a return, or the store may have difficulty identifying merchandise that is no longer in stock. If you act within 10 days following the holiday, you have a decent chance of getting a credit or making a successful exchange.

--Turn to the store manager. "Should you find a salesperson unhelpful, take it to the next level," says Holly Cherico, vice president of communications at the Arlington, Va. Council of Better Business Bureaus. The store manager has discretionary authority and is likely to be concerned about customer relations. And don't forget to lay on the charm in your negotiations.

--Find out how long a merchandise credit is valid. Even if you have a receipt, some retailers don't give cash refunds. So if you get a credit slip, make sure that it doesn't expire next week.

--Beware of hidden costs. When returning a gift to a mail-order firm, you will likely have to pay the shipping charges. But before you do that, check whether the company will pay for sending the replacement to you. Two-way shipping charges add up, and there are few things less welcome than the gift that keeps on costing.

--Anamaria Wilson