Online shopping bots can connect you to dozens of retailers selling the product you seek, sometimes at significantly different prices. Among the better-known bots are BizRate, Buy.com, DealTime, Froogle, MySimon, Shopping.com, Shopzilla, and Yahoo. BizRate and Shopzilla are affiliated, as are Shopping.com and DealTime, and you’ll generally get the same results in each of those pairs. (ConsumerReports.org offers a Shop Online tool in conjunction with Yahoo, but neither it nor Consumers Union, its nonprofit publisher, receives any revenue from merchants or from Yahoo.)

We haven’t formally rated bots, but our reporter did take 10 of them for a spin recently, shopping at each for the same digital camera and plasma TV. We found you’ll have a more successful bot experience if you follow these steps:

1

Try more than one. Different bots scan different sets of retailers, which will sometimes overlap. If you use two or three of the better bots, you’ll find results from dozens of merchants.

2

Sort by price. Bots often make their money by charging the stores they search a per-click fee, and some put retailers that pay a premium at the top of the results list, whether or not they have the best deals. So check whether the bot lets you sort by price.

3

Get the real deal. Shipping and taxes can add substantially to your bill, especially on items such as TV sets. And not all retailers calculate shipping the same way. To compare what you’ll really pay, use bots, such as MySimon and Shopping.com, that calculate both based on your ZIP code and then let you re-sort by total price. Also check on guarantees. Most bots make no guarantees regarding price, product quality, or even the reputability of the merchants. Once you decide to buy from a listed retailer, the deal is between the two of you. One site that promises the lowest price is Buy.com, but its guarantee is limited to a few specific vendors.

4

Know what you’re buying. Read the listing carefully to see whether you’ll be getting new or refurbished merchandise (see overview). If one retailer’s price is inexplicably lower than everybody else’s, odds are it’s selling refurbs. Also check whether the item carries the full manufacturer’s warranty. Some gray-market electronics, not intended for sale in the U.S., will lack one.