Does the store:
- Let you just buy what you want? Once you've finished looking for your product, does the store let you just buy it, or does it keep offering you alternatives--that is, trying to sell you something else? This a bad sign because it tells you that the store doesn't care about your time. Exception: "you might also like..." can be a reasonable thing for books, CDs, DVDs, and so on.
- Ask a price comparable to market, or does it seem low? If the price is substantially lower than most other places, chances are there's a catch. Perhaps many customers return the product, and the store charges a fee for this. Perhaps the product is counterfeit, stolen, or imported to the USA without the manufacturer's permission and has no useful warranty ("gray market").
- File your credit card numbers? This is a risk to you, and also a sign that the store is trying to promote impulse buying.
- Link its return policies up front? Can you locate their return policies on their web site at all?
- State shipping prices up front, or do you have to go all the way to the end of the purchase process before you find out what the prices of the shipping options are? Concealing the shipping price until late in the sale is an indication that part of the store's profit is made by padding the shipping price.
- Does the store tell you where they will ship from, so you can estimate ground shipping times?
- Does the store try to offer you an expensive loyalty plan as part of the deal?
Some general warnings; these apply everywhere, but are especially significant in online shopping.
- Never buy unbranded high-power (Li-Ion or NiMH) batteries--poor quality control can make these explosive. There was a recent luggage fire that involved a laptop battery.
- The lifetime of a battery is reliably predictable by the manufacturer; in batteries, cheap is expensive, a theme I will be croaking about in the future.
- Most extended warranties are far more expensive than they are worth. Unless you can't sustain the financial risk of a failure, or need the higher level of service that some manufacturers offer to extended warranty customers, don't go there. (Consumer Reports on extended warranties.)