Jewelry tops the wish lists for more than a quarter of consumers this holiday season, according to the National Retail Federation. And some of the biggest bargains can be found online -- if you don't get ripped off.

Shoppers are growing increasingly at ease buying bling online. While in-store jewelry sales have been growing roughly 4 percent a year in recent years, online sales have risen on average 20 percent a year over the past five years, says industry analyst Ken Gassman of Richmond, Va. Online jewelry sales are expected rise to $2.2 billion this year from $1.7 billion in 2004, according to Jupiter Research, out of the overall $57 billion jewelry industry.

Whether buying from a national chain or an individual seller, the first step is always research. Few consumers "really know what a fair price is anymore, and there is often high buyer's remorse," says John Baird of Blue Nile, a big online jewelry retailer.

Diamonds should be certified by independent labs like the Gemological Institute of America or the American Gem Society. Both also offer tips on buying and evaluating diamonds and gemstones at their Web sites gia.edu and americangemsociety.org. Insist on viewing the certification before you purchase. A reputable company should be willing to email a PDF.

There are a few other online resources that steer you through terminology and pricing. Bluenile.com offers a "build your own ring" tool that lets you test possible combinations of diamond cuts and settings, while explaining the lingo. The site also has a broader "education" page of jewelry-related primers. EBay, the auction Web site, also offers a sprawling array of educational tools and specialized information at reviews.ebay.com; click on "jewelry & watches," located part-way down the page.

But while eBay can be a valuable resource for research, when it comes to shopping there, be careful before buying: Individual sellers have come under fire in the past for trafficking in knockoffs. In 2004, Tiffany filed a lawsuit against eBay related to claims that eBay wasn't delisting sales of counterfeit Tiffany products. The lawsuit, filed in Manhattan federal court, is still pending.

Officials at eBay (which offers thousands of pieces, ranging from Mickey Mouse watches to estate jewelry) acknowledge scams are a possibility and caution consumers to research a product and its seller. "You have to be careful," said Sandra Graham, an official at the company. Avoid sellers with positive ratings below 99 percent, as well as those that don't provide a physical address or a telephone number.

No matter where you shop, apply the common-sense rule: If it looks too good to be true, it probably is.

After the jewelry arrives, take it to an independent appraiser -- not a jewelry store -- for a second opinion. (Jewelry stores may have an incentive to argue the item was overpriced in order to make a sale of their own.) For about $50, an appraiser can examine the piece and make sure you didn't overpay. For big purchases, the appraiser's valuation might be important for insurance, too.