1. If you're making an online purchase, don't hesitate to contact customer support if you have an issue. By contacting customer service before making your order, you'll find out how helpful customer support is and exactly how quickly they respond. This can be useful information to have in case something goes completely wrong after you've made your purchase.
2. Always save copies of your orders and receipts from online purchases. Many stores will redirect one to a page after you've submitted a purchase detailing anything that was bought, customer information, the prices, etc. You should either print a copy of this or save a copy to your computer in case any issues arise before the end of the return period. Make sure to save any emails regarding your items' status or correspondence with the company regarding your orders, too.
3. When you are searching for a spot to buy a specific thing and not one of the results seem to be from familiar retailers, you ought to be hesitant about entering your details. Look for security signs from Verisign or Cybertrust, so that you know the retailer is not out to take your cash.
4. If you're considering buying a product online, browse the reviews. The reviews off their people that have used the product should be able to give you a great idea about the product. You might be able to find out the quality of the product, if this worked as described, and if you should create the purchase.
5. Ensure that you're entering your payment details on a good site. Look for "https://" in the URL from the site that you're seeking to buy something from. If you don't see that or no symbol of any website security, then it's probably a wise idea not to trust those people along with your account information.