Sold! Talking toy Chihuahuas. Tiffany lamps. A 1987 Mustang convertible. Survivalist gear, in case those predictions of Y2K chaos pan out. You name it, it's among millions of items up for auction on the Web every day.

HOW TO SELL, HOW TO BUY If you're a seller it works like this: You post a description of the item you want to sell, usually along with a photo. You set certain parameters such as the ending time of the auction, and the minimum bid you're willing to accept. Bidders all over the world can then vie for your items. When it's all over, you contact the highest bidder and the two of you agree on exchanging payment for the goods. If you're a buyer it works like this: You can log onto a site and peruse items posted by sellers. When you see an item you're interested in, you can place a bid online. Some sites have tools that let you set the most you're willing to spend for an item and the system will bid automatically for you, or alert you when someone outbids you. If you snag the high bid, you negotiate with the seller to exchange money for the goods.

On one recent afternoon there were some 1.3 million items on the auction block at eBay.com, which has 1.2 million registered users. Auctionuniverse.com, handles about 20,000 auctions a day; at OnSale.com the auction gavel falls on some $700,000 worth of transactions a day.

No doubt about it, online auctions are hot, particularly the sites where individuals sell directly to other individuals. But, what, you may be wondering, can you really find at these virtual flea mar- kets? Treasures or junk? How do you even find stuff to bid on, and protect yourself from rip-offs?

Most people are honest, and the quality of merchandise put up for auction is usually fairly good, say some buyers and sellers who frequent auction Web sites. Others, however, complain about sellers who don't deliver what they promise, or buyers who write rubber checks.

''I've done maybe 500 transactions on eBay,'' says Deborah Burke, who runs a Newton-based business that buys and sells antique clothing online. How many of those deals have gone bad? ''Just five,'' says Burke. The virtual dealing has been so good for Burke, she recently left her ''day job'' with a management-consulting firm to buy and sell goods online full time.

Burke, who runs her own Web site as well as trading on eBay, has high praise for the quality of merchandise up for auction there. ''I could travel around in my car from antique shop to antique shop, or auction to auction for the rest of my life and not see what I see on eBay in a week. It's extraordinary items that are accessible to me as long as I want to pay the price.''

Of course, not everything listed for auction online is exactly museum-quality stuff. There are plenty of groovy rotating disco lights, nodding head chihuahuas, and the usual junk you'd have to pick through at any garage sale.

Mark Dodd, who runs a Web site called auctionwatch.com, which tracks auction Web sites, agrees that you can find quality items on auction sites. Although, he says, some naive bidders overpay.

''However, if you're aware of the value of something and you're patient and realize that there will probably be another one coming online at some point, you can get very good values,'' Dodd says. For example, he secured a vase for $240 ''that's easily worth $750 to $800.''

Dodd says he started auctionwatch.com last June as a forum for auction site enthusiasts to freely chat about their bids. ''I was frustrated that they (an auction web site) put a choke-hold on communication between bidders. That you couldn't say to another person that they're perhaps going over retail, or that they could find something cheaper somewhere else,'' says Dodd.

Visitors to auctionwatch.com hold spirited discussions on electronic bulletin boards. The site carries links to 280 auction Web sites, and under a section called ''The Buzz'' there's a running list of links to news stories about anything related to online auctions.

It's clear from the intense discussion boards at auction-related Web sites that the people who are into this are really into it.

''You hang out in the chat rooms,'' sayd Dodd. ''You start developing relationships, before you know it, they're your friends and you're excited about getting online. You tie the addiction of the Internet up with these chat rooms and the community aspects of auction sites ... ''

And you're hooked.

Burke agrees, but says she doesn't bother with bulletin boards and chat rooms. The thrill is strictly in the buying and selling. ''As soon as you go in there, you are absolutely hooked.''

''There's a term called 'auction fever,' says Burke, describing the state that overcomes bidders at live auctions. With online auctions running 24 hours a day, and thousands of items coming up for bid daily, ''It's a constant auction fever. You think: Oh my God, what am I going to miss? What's up there?''

''There's an excitement about it,'' Dodd says. ''You get online and you're competing against someone. You see the clock ticking down and it's going to expire. It can be pretty exciting.''

Ron Rappaport, an analyst for Zona Research of Redwood City, Calif., reaches back to hunter-gathering times to explain the attraction some males have to online auctions.

''They go out, they find a good bargain, they hunt it, they kill it, they take it home. And then they're proud of it. They hold that carcass up in front of other Web users and say, 'I got this same computer for 20 bucks less!'''

Some auction enthusiasts, like Burke, have found this world so alluring that they've devoted themselves to it full-time. Says Burke, ''I know a guy who goes over to France, finds antiques, brings them back to the States, and then auctions them on eBay. He makes a really good living.''

But Burke cautions, ''It's a lot of work. You have to find the stuff, take the pictures, get it up on eBay, follow through, get the money, pack up the goods, get it to the post office. It's a long process. Right now I have probably 25 to 30 items up.''

But what about the darker side of all of this online bidding and buying? Complaints about rip-offs at person-to-person auction Web sites make up more than half of the 300 Internet fraud reports received each month by the National Consumer League in Washington, D.C.

eBay has recently been stung by complaints from users that they haven't been tough enough on fraud. The company says cases of fraud are rare - only about 27 in every 1 million transactions - they recently announced plans to beef up their ''Safe Harbor'' program, offering insurance policies of up to $200 on eBay transactions that will cover both buyers and sellers. And a new ''Verified eBay User'' program will make it easier to believe people are who they say they are.

Tips for safe bidding on the auction sites It's safest to do business with auction sites that guarantee transactions with insurance policies in the event that deals go bad, and that verify buyers and sellers are who they say they are. Before you jump in, take a few minutes to peruse the policies and rules at an auction Web site. Don't assume that the same protections that apply in regular retail outlets apply in cyberspace. Which comes first? Do you pay for an item, and then the seller ships it? Or does the seller ship the item so that you can check it out before you pay? It's a big issue in person-to-person auctions. If you're skittish about working out this kind of deal there are intermediary services such as iescrow.com, trade-direct.com, and tradesafe.com that can help you close the deal, for a fee. The buyer sends the payment to the escrow service, which verifies the payment and alerts the seller to ship the item. Once the buyer receives and inspects the goods and says OK, the escrow company releases the payment. Check out sites such as auctionwatch.com or honesty.com which carry news about auctions sites and have a following among buyers and sellers. If something's fishy going on, there's likely to be buzz about it on these third-party Web sites. Time Savers: Don't overlook tools at some Web sites that automatically place bids for you, or alert you when someone outbids you to boost your chances of getting the winning bid. Try Web sites such as bidfind.com, or click the Auction link at Lycos.com where you can search hundreds of auction sites at once for items you're interested in bidding on, or to see what other sellers are getting for comparable items.

At Auction Universe, shoppers who pay by credit card are offered a money-back guarantee through the site's Bid Safe program for a fee of $19.95 a year. Other sites offer varying degrees of protection to buyers and sellers through insurance policies and strict registration requirements.

The online auction community does some self-policing as well, dropping a dime on anyone who's not on the up and up through bulletin boards, and on sites where they're allowed to comment on transactions.

Once you've gotten over the quality of the goods and safety issues and are ready to bid or sell, finding an auction Web site can be as simple as typing the keywords ''online auction'' into a search engine. It's all there, from antiques to wine.

Click a few links and you'll find that businesses are auctioning off surplus and refurbished items to consumers. Individuals are emptying out their attics on person-to-person auction sites. Businesses-to-business bidding for goods and equipment is growing, too. Stock prices of popular sites are going going gone through the roof.

''If you're a retailer and you announce an auction site, your stock goes up 50 percent,'' says Dodd. He was speaking in jest, but just barely. Last month, shares of the renowned auction house Sotheby's shot up 28 percent when the company announced it will join the online auction frenzy this summer.

eBay, among the hottest of the red-hot Internet stocks has soared from an intial public offering of $18 to more than $200 a share. And when Ticketmaster Online-City Search announced a $54 million deal last month to acquire City Auction, a service that conducts regional auctions, shares of Ticketmaster gained 10.625. Retailers turned ''E-tailers,'' such as Sharper Image, and Egghead, and Internet ''portal'' sites such as Yahoo! are raising the auction gavel on their sites, too.

What does all this mean for the average online consumer? Possibly better protection from fraud as businesses vie to get you to feel more comfortable about bidding early and often at their virtual auction houses.

But don't expect the ''Nodding Head Chihuahuas,'' or revolving disco lights to disappear. What's a flea market without those kinda gems?

Michelle Johnson, an Internet consultant, is a former editor for the Boston Globe. She can be reached at mijohn@mail-me.com.