Before making computer-related purchases, think carefully about what you want, what you really need—and especially what you don’t need.

Our ratings of area computer stores will help you find retailers that employ sales staff that can provide sound advice—and steer you away from stores where they can’t.

If you’re buying a laptop or desktop computer, because there aren’t big differences in track records for reliability among the major brands, compare performance, features, and prices offered by several manufacturers.

Once you decide what you want, shop for price. If you’re considering an Apple product, you’ll find little store-to-store price variation (unless you buy used). You’ll also find only modest price variation for software. But for most other manufacturers and purchases, if you shop around you’ll encounter substantial price variation among brands and considerable store-to-store price differences for specific models.

When Checkbook’s undercover shoppers surveyed prices at popular online retailers for 33 devices, we found that some outlets on average charge as much as 20 percent more than their competitors for the same stuff. Among the outlets our researchers shopped, we found that Amazon and NexTag offered the lowest prices.

Pay with a credit card. The Fair Credit Billing Act and policies of credit card companies enable you to refuse payment made with a credit card for merchandise that is unsatisfactory or undelivered.

Don’t bother paying for an extended warranty. For most shoppers, these warranties are bad deals.