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Whether you're downsizing your own household or dealing with a relative's estate, selling a lifetime of stuff can be stressful. Who to call for help? Below, a rundown of the liquidation industry's key players.

Estate Sale Companies

LICENSED? No.

WHEN TO USE: For a house-full of low to mid-level stuff.

COST: 25 to 35 percent of gross sales

COMMENT: This highly fragmented industry has no barriers to entry; anyone can hang out a shingle and start pawing through mom's jewelry. To avoid fly-by-night operators, says Julie Hall, founder of The American Society of Estate Liquidators, it's important to get documentation: multiple references, a contract, evidence of insurance and examples of previous post-sale accountings. And whatever you do, pros say, don't throw anything away, since hidden treasures can be lost and small items add up fast. "The underbrush of the estate can account for 50 percent of the sale," says Martin Codina, CEO of San Francisco area-based Fine Estate Liquidation.

Appraisers

LICENSED? No, but most are professionally trained and certified in valuation.

WHEN TO USE: When you need official valuations for insurance or the tax man.

COST: $100 to $300 per hour

COMMENT: Generally the most highly trained professionals in the estate universe, many appraisers complete certificate studies. And those affiliated with industry groups like the Appraisers Association of America or American Society of Appraisers must adhere to industry standards requiring disclosure of any ethical conflict. The biggest offense: valuing, then offering to buy, your stuff.

Buyout Services

LICENSED? No.

WHEN TO USE: When you're in a hurry to clean out and sell a house.

COST: All over the map.

COMMENT: These are the guys who will haul away the contents of a home, often after making a 20-minute walk-through appraisal. (Many liquidators and auction firms offer the service.) If they see nothing of value, they'll charge a few hundred bucks for a cleanout. If there's worthwhile stuff, they'll offer a blanket fee and then resell as much as they can. Critics say buyout folks often lowball their estimates, and fail to disclose hidden gems. But buyout pros say they take big risks, and can get burned when items don't pan out, value-wise.

Auction Houses

LICENSED? In some states.

WHEN TO USE: For higher-value art, antiques and collectibles or big items like vehicles or farm equipment.

COST: Generally 10 to 20 percent of the final sale price

COMMENT: Auctioneers range from swank houses that handle the finest, rarest stuff to "have gavel, will travel" services that hold sales on site at your home or farm. But competitive bidding isn't always so, well, competitive. Smaller auctions with heavy wholesale traffic sometimes attract dealer "cartels," says David Rago, president of New Jersey-based Rago Arts. Their tactic? Deliberately suppressing prices by agreeing not to bid against each other, then wrangling later amongst themselves.

Senior Move Managers

Licensed? No.

When to Use: When you're paralyzed by your possessions or need to move suddenly to a care facility.

COST: $40 to $150 per hour

COMMENT: The focus here is on more than just liquidation, say professionals in this burgeoning field. (The National Association of Senior Move Managers says its ranks have grown almost tenfold since 2006, to more than 600.) Working like project managers for a move, they handle everything from organizing donations and sales to mapping out and setting up the new space.