Penny Catterall is helping mom Bilha Bryant winnow her collection of foreign objects before moving to an apartment.

The baby boomers, long known as master acquirers, are now learning a new skill: getting rid of excess stuff. Some are empty nesters moving to smaller digs. Others are helping their own aging parents sort through belongings before a move or are disposing of items after a parent's death.

Call it downsizing, rightsizing or deaccumulation. Whatever the lingo or reason for selling off personal treasures, your goal should be the same: to get as much as possible for things, with as little family strain as possible.

Here are ten tips to help.

### 1 Accept that downsizing is tough

Penny Catterall works as a professional organizer out of her Bethesda, Md. home. Now she is helping her own 77-year-old widowed mom, Bilha Bryant, winnow down possessions filling a five-bedroom house in advance of her move to an apartment in Friendship Heights, a pedestrian-friendly neighborhood near Catterall's.

In May mother and daughter staged a one-day private sale at Bryant's Washington, D.C. house of items collected during her late husband's 33-year career in the foreign service. Catterall promoted the sale of embroidered textiles from India, Afghan tribal jewelry, African masks and Korean celadon vases on her neighborhood's Yahoo ( YHOO - news - people ) Group. Total take: $4,000.

Yet even as an organizing pro, Catterall found the event emotionally draining. "I had the most massive migraine," she said the day after the sale. "It was very personal."

### 2 Do your homework

Don't hold a tag sale without doing some due diligence, or you could be hoodwinked. Professional "pickers" haunt such sales looking for valuable items sold by the clueless, warns Joy Berus, an art lawyer in Orange, Calif.

Before her mom's house sale Catterall spent hours researching items online. Some things were easy. She sold a vintage Klepper folding kayak found in her mom's attic on Craigslist.

She also asked dealers her father had worked with to help her assess which items were tag-sale goods (under $500 in her case) and which could bring in more sold elsewhere. She ended up shipping a pair of Chinese Imperial bowls her dad had stored in the basement to a Boston dealer; their sale netted enough to cover two months of her mom's rent.

### 3 Call in an appraiser

If you don't have any idea of what you've got, consider paying the $150-an-hour (and up) fee for an appraiser of "household contents" or "decorative arts" to visit your home. The appraiser shouldn't be bidding for your items or working on commission and should be able to judge quickly if you've got reproduction furniture or real antiques.

An expert consult could also preserve family peace. Arcadia, Calif. appraiser Nancy Martin was called in by two sisters feuding over who would get their late mom's (supposed) French 18th-century chest of drawers. Martin saw immediately that the chest was a common Baker reproduction. The real antique, a piece both sisters detested, was on another wall of the house. She suggested they sell it, buy a second Baker chest so they'd each have one and split the excess cash.

### 4 Be wary of family lore

Just because your late grandma was told something she bought was valuable, that doesn't mean it is. "You don't know how many things supposedly belonged to George Washington,'' Martin sighs. Richard Wright, who runs an auction house in Chicago specializing in modern design, says families often call about a molded plywood Eames dining chair. "We'll get this big windup, ‘We have a chair that's in the collection at MoMA,' and we have to tell them the chair was mass-produced and theirs is probably worth $300,'' he says.

On the other hand, family members may have an object they use daily and don't realize is valuable. In Brooklyn personal property appraiser Frances Zeman spotted a matte green Arts and Crafts Grueby pottery vase worth $10,000 jammed in a cabinet under the kitchen sink with glass vases from flower delivery services.

### 5 Don't junk that Buck Rogers patch

A lot of stuff that is salable appears to be "trash to the uninitiated eye,'' says Richard Meliska, who with his wife, Merrill Essex, owns Essex Antiques & Collectibles in Evanston, Ill. The couple, a former banker and marketer, do estate clean-outs, helping clients sort possessions into throwaway, donate and sell piles. (They typically work on commission ranging from 20% to 50% of sales proceeds.)

The throwaway pile includes old newspapers, decayed firewood, moldy clothing and cracked everyday china. The donation pile includes bed linens, Tupperware, stuffed animals--things you might get just a few bucks for at a tag sale but that could be of use to the right charity. In the next pile are items worth $25 or more. Then the couple determines the best way to sell each item, including sales to specialized dealers, on consignment to a regional auction house and through a listing on eBay ( EBAY - news - people ).

What looks like junk but isn't? Meliska rescued a Buck Rogers sweater patch and a box of tin toys that a client had put in the trash pile. The patch alone just sold for $900 (it would have brought $3,000 in better condition), and the toys sold for $100 to $200 each.

### 6 Call in an auction house

Auction houses will also send out specialists to review your household contents and suggest items you might consign. Some regional houses, like Quinn's Auction Galleries in Falls Church, Va., take general high-end household contents; others specialize in certain period items. An auction house might take your lower-value items only if you agree to no reserve--meaning you must sell no matter how little is bid.

While at an estate sale you have a limited audience and you set the price, at auction you can reach an international audience and the price can be bid up. At a recent Scandinavian design sale at Wright, a pair of walnut-and-birch twin beds with slatted headboards by Danish designer Finn Juhl, estimated to sell for between $4,000 and $6,000, fetched $20,000 instead. The downside: A third of the lots went unsold.

### 7 Donate and deduct

Bags of old clothes and old furniture can be left out for the Salvation Army or Goodwill to pick up. Local social service agencies often keep lists of nonprofit needs--e.g., a fax machine, a desk. Aside from the satisfaction of giving, you get a charitable deduction on your tax return--assuming you itemize. Note: You must list anything you donate worth $500 or more on a Form 8283 attached to your 1040. You'll need a qualified appraisal to deduct any item worth $5,000 or more. If the item is valued at $20,000 or more, you need to attach that appraisal to your return.

### 8 Pass down some heirlooms as gifts

You can give away up to $13,000 a year in cash or items to as many individuals as you like without worrying about paperwork or eating into your lifetime exemption from federal gift tax--that is, the amount you can give away without owing gift tax. (That exemption is a whopping $5 million for 2011 and 2012 but will fall to $1 million in 2013 if Congress doesn't act.) "You can give away a lot of stuff, keep it in the family, and there are no tax costs," says Carol Harrington, an estate lawyer with McDermott Will & Emery in Chicago.

Once you go over $13,000 per person, you must file a federal gift tax return. It may be worth it, if you're passing on family treasures your children can use and enjoy now--and that aren't worth a lot more than you paid for them. If they are worth more than you paid, see the next point.

### 9 Consider capital gains

Most personal items bought at retail depreciate enormously. A set of china you paid $5,000 for might go for a few hundred dollars. Jewelry listed on your insurance policy at replacement value could bring as little as 30% of that value if you sell it. The upside: If you don't have a gain, you don't owe capital gains tax. If you do sell art, collectibles or personal property at a gain, however, that gain is taxed at 28%. One problem: If you can't prove your basis (meaning what you paid for the property) the Internal Revenue Service can assume it's zero.

On the other hand, if you hold on to something until you die, your beneficiaries get a step-up in basis--meaning its new basis is what it's worth when you died. So if you have an item that has appreciated or that you can't show the basis of (and your heirs might someday sell it) you probably want to hold it until your death.

### 10 Reduce paperwork for your heirs

Under current law, on Schedule F of the Form 706 estate tax return, an executor has to list the value of the deceased's household goods (this includes jewelry, furs, silverware, books, statuary, vases, Oriental rugs and coin or stamp collections). Any item valued in excess of $3,000 or any collection valued in excess of $10,000 must be appraised and listed separately. That's another good reason to pass down family treasures before you die--if, that is, they haven't appreciated or are unlikely to be sold by your heirs.

#### Treasures Hiding In Your Attic

Don't pitch stuff too fast. What's stashed in your attic, basement or garage could bring in cold cash.

Gold And Silver Jewelry
  The real stuff is often thrown in with costume jewelry in a dresser drawer. With gold and silver prices so high, even an ugly piece that's not an heirloom can be sold for scrap value. Get bids from a few gold-buying stores in your area.
"Tacky" Heirlooms
  You probably won't find a Tiffany lamp worth $80,000, but don't underestimate the value of old stuff (even if it's not to your taste) lurking in the ordinary, modestly priced house of an older relative.
Old Building Supplies
  Instead of paying someone to haul away and trash the old building supplies in your garage, donate them to Habitat for Humanity ReStore, which picks up old decking, lumber, windows and even toilets. You get a tax deduction.
Vases
  Valuable vases tend to get overlooked. This Venini vase worth $7,000 was rescued from an impending tag sale by Richard Wright, who owns a Chicago auction house. Another expert found a $10,000 vase jammed in a cabinet under the kitchen sink.
Old Posters
  Vintage travel posters (used as advertising for airlines, ships and trains) and movie posters can sell for $500 and up. An estate liquidator found posters worth $23,000 rolled up in a closet and a basement.
Electronics
  Online outfits like Gazelle.com and uSell.com buy cellphones and other gadgets to refurbish and resell. List your high-end audio gear for sale at AudiogoN.com. Donate dated items to the Salvation Army.
Oriental Rugs
  Don't sell those worn old carpets at a yard sale until you know for sure they're not worth much. Call an appraiser. You may have a rug worth a few hundred dollars or a Persian Lavar Kerman worth thousands.